Introduction to Aerodynamics

so welcome to introduction to aerodynamics this is an introductory course on aerodynamics the subject matter of aerodynamics is finding the or determining the forces and moments that acts on any body that moves through a feed in our case we are mostly interested in air but the basic principles are same irrespective of what fluid it is considering the body as an aircraft see one aircraft moves through a body it experiences certain force as you know that aircraft exerts forces on the air and air are in turn exerts forces on it and these force and moments and estimation of their contribution to the motion that is what is the subject matter of aerodynamics since these force and moments comes because of the pressure and viscous stress that is develops on the surface of the aircraft so aerodynamics try to determine these pressure and viscous stresses on the surface and of course these pressure and viscous stresses are dependent on the overall flow so you can say that aerodynamics is the study of the flow about any body that is immersed in a fluid and moving through it we are mostly interested in the body of aircraft and if we consider aircraft let's say what are the forces that acts on an aircraft we know that there is a by own sea force but usually the buoyancy force is so small that it is hardly considerable when compared to the total weight of the aircraft and we can neglect it for further motion now aircraft considering the simplest possible flight which is that aircraft flying in a straight level flight that it is going straight and keeping its altitude more or less fixed under this condition you know that the forces need a balance the weight force needs to be balanced by some pose similarly the engine thrust is also balanced by some other forces and these forces are in this configuration of flight are known as the lift and drag force that is on the aircraft is in a steady level flight it is balanced by the lift force and the thrust is balanced by a drag force both of these forces are in aerodynamic nature that is they comes because of the relative motion of the aircraft and the air or the fluid now if there is any disturbance in the flight of course the moment develops and the configuration of the aircraft changes the force coming from the pressure distribution and viscous stress distribution and they are distributed over the entire surface of the aircraft okay it's not necessarily a trap it can be any body which is immersed in fluid now as you know that a distributed force can be represented by a system of force and moments same thing can be done here also and these force and moments that can be resolved in any three mutual orthogonal direction if we consider these three mutual orthogonal direction are like this but if you remember this direction the let us call it X axis the x axis is along the relative wind it is along the relative wind that means it is along the direction of the relative velocity between the body and the feed is neither horizontal nor vertical or anything it is along the direction of relative velocity between the body and the fluid so as an example if we consider that an aircraft is moving in atmosphere which is at rest then the relative wind is simply the direction of or opposite of the direction of the aircraft speed so in that case the x axis is opposite to the direction of the aircraft velocity if an aircraft is flying through an atmosphere at rest the x axis is along the opposite of the direction of aircraft velocity or aircraft speed however in general we'll call it the direction of the relative wind the x axis is related in the direction relative to the wind and let us call at this stage the Jade axis which is up or but not vertical it is normal to of course the x axis so it is upward but it is not vertical since x axis is not hot horizontal the Jade axis is not vertical and the y axis is okay which is perpendicular to the plane formed by X and jet usually for an if we consider the body to be an aircraft we call it the direction to the right wing right side of the wing with respect to the pilot so the right side can be with respect to an observer the observer may be I found observer may be behind so of course the right side will change series right side with respect to the pilot usually that is called the starboard side these names came from shipping where they have the left side is usually called the port side as ships comes into a port its left side is usually faces the port towards the port so that left side is called the port side and the right side is called the starboard side and same nomenclature is used here in aircraft also so the right side of the aircraft is called the starboard side and the left side is called the port side so now the axis system that will that is usually followed in all aerodynamics you will study in other subjects the aircraft motion the dynamics of complete aircraft and in that context we will define various type of axis system but the axis system that is used in aircraft so the aerodynamics is like this the x-axis is along the relative wind jet axis is normal to x-axis upward positive and y-axis is normal to the plane of form by X and jet and to the starboard wing side is positive now if we resolve the force in these three direction in these three direction the component in the x direction is called the drag force so you see that the drag force is a component of the force along the relative guen direction the drag force is along the relative wind direction and again taking that example that aircraft moving through atmosphere at rest then it is opposite to the direction of aircraft speed the drag force is opposite to the direction of the velocity of the aircraft the force which is normal to this x-axis that is along that direction is called lift so lift force is normal to the relative wind it's not vertical lift force is not a vertical force it is normal to the relative wind and the force in the y-direction is called side force it is positive if it is towards the starboard if its reaction is towards the starboard it is positive the three moments the three moments about these three axis are called as pitching moment if it is about the y-axis the peak let's come from the moment about x-axis the moment about the x-axis is called rolling moment now what will this moment do as you can see that if an rollin moment acts on an aircraft it will try to bring one wing of the aircraft down with respect to the other wing one we will go up the other wing will come down that is what the rolling moment will do if a rolling moment acts on an aircraft its following will come downward the other room will go up if the starboard wing goes down the rolling moment is called positive similarly the moment about the y-axis that is an axis which is along the length of the wing or almost along the length of the wing a moment about that axis is called the pitching moment and what will be the action of this moment you can see that if there is a moment acting about this axis I the other nodes of the aircraft will go up or go down if the sense of the moment is such that the nose of the aircraft goes up then it is called a positive pitching moment similarly hearing moment a moment about the z-axis which can be called approximately vertical it is not the vertical direction but approximately vertical direction now a moment about it what will you do it will take the nodes to the left or right it will tend to move the nodes towards the left or towards the right if if it tends to move the nose towards the right that is towards the starboard side the young moment is taken as positive now so we have defined the three aerodynamic forces and aerodynamic moments all the forces and moments comes because of the relative fluid flow over the body so this is also another basic premises in aerodynamics that in aerodynamics we consider the body is at rest while the fluid is moving in the real world if you look to an aircraft it is the aircraft which is flying that Moscow is more or less at rest there might be a small wind which is say negligible as far as the speed is concerned is negligible to the speed of the aircraft while and aircraft flies at a speed of some 700 800 or 1000 kilometer per hour the wind is about some 4050 even less than that sometime 20 kilometer per hour so which is negligible so usually it is in the real life the aircraft moves that air is at waist that most fair is rate at waist in aerodynamics we consider it the other way it is always taken that the body is at rest and the fluid is moving through it that is you consider the relative velocity and all these forces this lift drag pitching moment going moment all comes because of these relative flow the relative velocity because of the flow field of course that is the subject matter of aerodynamics to analyze that flow field and to obtain these forces now think about an aircraft which is flying straight and level 100 flying straight and level of course no moment is acting no moment is acting and again as long as it flies straight and symmetric you see that the side forces or this Ewing and rolling moment they do not act the joining moment and side force rolling moment they come into picture only when there is an asymmetric flight if there is no asymmetric fight the forces or moments do not come into picture so during the flight time of an aircraft most of the time the aircraft is not experiencing any going moment or rolling moment neither any side force of course there are certain situation when all of these are acting or even these young moment rolling moment on side forces are acting but most of the time during its flight only lift and drag and possibly teaching moment acts now before we move to the real subject of aerodynamics lists give sudden important information as far as aircraft is concerned you know an aircraft consists of different components the most important components of an aircraft are it's useless the wings horizontal and vertical tails and engine these are the most important component of an aircraft the horizontal and vertical tail they are also like wings and so the most of the conventional aircrafts as you can say perhaps we can sketch that they look something like this this is what is the side view of an aircraft if you see it from side this is what it looks like a side view for this main body is called the fuelers or it houses all the important payloads if it is an commercial airliner this is where all the passengers will be this is the wing as it appears in a side view of course in a side view you will see only a cross-section of the wing this is called the horizontal tail plane of the aircraft here also you see only the cross-section and this is called the vertical tail and see there will be an engine usually attached to the wing so you can name it this you sorry the wing the horizontal tell and this is vertical tell this is what is the the plan of you here you have shown the wing as something like trapezoidal but that is not necessarily true that there we has to be travel the plan form the plan form can be of various shape it can be even a triangular what is called the delta wing and see we have shown here the leading edge this is called the leading edge and this is called the trailing edge so the leading edge of the wing we have shown here as a straight it is not necessary to to be straight it can be curved so this is our representative D of the aircraft or representative aircraft you can say a conventional aircraft there are many non conventional aircraft where you can clearly identify all these different components in such a manner now as far as the aerodynamics is concerned the most important component of the aircraft is the wing because these produces perhaps more than 95% of the total lift that the aircraft produces for a conventional aircraft almost the entire lift comes from these wings so this wing is the most important aerodynamic component tell is of course a small wing the horizontal tail vertical tail is a vertical owing we can say now we have seen this cross-section of the wing which are the special shape usually it is quite thin the thickness is of the order of say of course it is a variable it is not that for all aircraft the wing thickness is same the thickness is of the order of something like say 10% 12% of the call may be then less now we will define what is the score and certain important definition which are required in the later stages of aerodynamics that will come forward the shape that the wing takes in its platform in its plan view is called its plan form the shape that the wing takes in plan view is called its plan form so in this case the plan form is trapezoidal so horny call the plan form of a wing it simply means that how how does it looks horny take its plan view okay that is how you take its projection in plan then the distance between one wingtip to the other wing tip that is the distance from here to here the distance from here to here is called the wingspan distance from left wing tip to the right wing tip is called the wingspan in doing so you see that we are considering even that part of the figures the wing is connected to the feelers so in within the fuselage the wing is not there doing is not extended but while talking about the fun we talk about the entire wing tip to wing tip as if the wing is inside the fuselage also another very important quantity is the planform area as you have seen that the plant form is simply the view that the wing takes in its plan view so the area of that plant view is the wing area now then there is a question that how you take the plan view of the wing as you can say that in the plan the wing is up to this to the fuelers so this is the plan in this case the plan view is say a trapezoidal so the area of this trapezoidal this two trapezoid but it is not exactly so it has to be extended within the wing within the fuelers that means while finding the wing planform area the wings will be extended up to this and the area of these to fill these two trapezoids not only up to the fuelers but to the center of the fuelers extend the plant view or plant form to the center of the aircraft and then find its area that is what is the platform area square root of sorry square of span / transform area is called the aspect ratio of wing the aspect ratio of wing is so span distance from tip to tip there are common aerodynamic notation for these quantities the span is usually denoted by B the span is usually denoted by B more or less an Universal notation the planform area is denoted by the word letter s capital S the aspect ratio most often denoted by a joint a are in some cases you will find only a also but most often it is used as a joint AR and that is the notation we will also follow it is simply B Square by s or denoted by C it is distance from leading-edge two trailing edge now you can see that in general the score is then changing is not fixed quantity and there are various mean calls defined one is of course a geometric mean curve the other is called the aerodynamic mean curve how do you define these geometric mean code it is obviously quite the smallest is to represent semi span half of the span smaller is stands for B by two now the wing we have already talked about wing tip the wing at the junction or at the central axis as you said that if we extend the wing to the center of the aircraft then the chord length at that that is cod it is called the wing root coming back to the told figure the wing root here so this is root this is tip this is leading edge this is trailing edge there will be a difference in the cord length or the tip and core length at the root and their ratio is called the taper ratio tip cod2 root core the ratio tip cod2 root core is called the taper ratio okay forgot to tell aerodynamic mean code the aerodynamic mean code is defined as if the wing is shift backward with respect to that is from the root to tip if it goes backward with respect to the say the y-axis then the wing is called a shift back wing and the angle between the y-direction and the leading edge is called the surfed back angle again let us with respect to this figure itself if we have this is the direction of the y-axis then this angle is called feedback angle eventually what we defined is specifically it is called leading-edge feedback it is called leading-edge feedback though we have called it sieve back because the feedback may vary at different that is the leading edge may have a different sweep angle than the trailing edge the trailing edge sweep angle will not be same as the leading edge and also if we take any other line on the wing at certain fixed percentage of curve then the sweep angle of that line may be different or rather in general they are different let us say that we think about a mid Cod mid-quarter location that is at every section on the wing we will look at the mid Cod and then join it by a line then we get a midcourt line again let us take it one particular wing cross-section only let us consider and let us say this is the direction of Y axis so this is leading a shape similarly this will be trailing a shape usually denoted by this and similarly let us say we have midcourt line that is at every station we are locating this line is passing through the middle of the core at every station or say think about the 25% quarter line so each line edge all the lines have different ship trim back and as we mentioned that in many cases they are craft leading edge itself can be a curved line and if it so happens then you can see that the sweep even on a particular line shape changes they are called variable-sweep geometry if the leading edge is curve then the sweep angle changes along the leading edge itself so they are called variable shift between No we'll come to this the section of the wing the section of the wing is called an airfoil all British English was aerofoil so sometime we may call aerofoil and nowadays in the American English it has become airfoil so both will be used we cross-section geometry this is what is unusual shape of air fall if we join it from leading edge to trailing edge the line joining it is called its core the line joining the leading edge to trailing edge is called the core and at any particular corage location if we have the distance between the upper and lower surface is called its thickness this is all the upper surface of their fault and this will be calling the lower surface in aerodynamics of airfoil usually this point or the core intersects the nodes node of the airfoil is taken as the origin of the axis system and it is conventional conventional to take the x axis along the power the study of aerodynamics usually the leading edge sorry the coordinate origin is placed at the point where the core intersects the nodes that is here and the x axis is taken along the curve and of course the their axis is normal to the most important quantity in aerodynamics you are saying that is called an angle of attack angle of attack it is the angle between the relative wind and the chord line if we call this is the relative wind we will be denoting it by u infinity Y will come later infinity and this angle between this and this is all alpha and remember that the force lift force is normal to this u infinity and the drag force is along u infinity for a supersonic use often the leading edge of the airfoil is also pointed oil for subsonic use the leading edge is smooth and round but for supersonic huge often the leading edge is sharp now we have defined thickness and core in aircraft almost all length almost all length parameters are non dimensionalized with respect to curve often it is mean aerodynamic curve or mean geometric curve either of them so let us say that the thickness or all other parameters of an aircraft will always be expressed in terms of percentage curved air faults are usually designated by their thickness so hone it is called that an airfoil is 10 percent thick meaning the air fall has maximum thickness of 10 percent of its core that is if the power of the airfoil is say 1 meter then the maximum thickness of that air fall is 10 centimeters if we called our fall as 10 percent thickness if the maximum thickness as you can see that the thickness changes from leading edge to trailing edge at the trailing edge the thickness become practically zero and the maximum thickness occurs somewhere ahead of mid curve depending upon the type of airfoil it is a mid curve if the power is if the core does not intersect or does not divide the air fall into symmetric hub okay that is upper half and the lower hub are not symmetric with respect to the curve then the air fall is called a Campbell fall then their fall is called a camber airfoil if if it is symmetric that is if it is exactly at the middle of their fall then therefore is called symmetric so the air Falls can be either symmetric or asymmetric which is called camber cambered CA in b e ra d camber Converter for you it is not symmetric about the hole early now in such a case of course you can see that you can imagine or you can construct a line which is exactly at the center of therefore at each section at each station you can think about the thickness and then take the midpoint and join all the midpoint and you will get a line which is just at the middle of their fall within the middle of their form so that line is called the mean line or camel line that line if we join the 50% of the thickness line at each station and construct a line that line is called the mean line or camber line if the mean line is above the curve then the air fall is called positively camula cambered that is when the mean line is above the cowl it is positive number if the mean line is below the curve it is negative camber usually all practical aircrafts are positive camber something else we missed that is a diadem what is it I head out see how an aircraft has two wings on its two sides on the left-hand ride and think about that for each wing if we think about the cross section all the cross sections are an airfoil all the cross sections are an or fall so thinking about that wing over the semi span at each each station it has its own airfoil now the power of each of these airfoil caught up each of these our fall may not be in the same plane if they are not in the same plane sorry then the wing is called a twister giving a geometrically twisting wing on the car at each section is not on the same plane then the wing is called a twister living and in such a case you can see that the angle of attack at each cross section will also be different the angle of attack at each cross section will also be different however if the power on the same plane then the wing is called untwisted and in such a case if the if all their faults are same or false then the angle of attack at each section will also receive a wing or aircraft is called a having dihedral wing when the two wings are not on the same plane in in a front view with a dihedral wing it will look like this so this is called at Hydra level and this angle is called the dihedral angle similarly the wing is such that it's tip is drooped with respect to the root then it is called anhedral the the opposite call is called anhedral where the tepees groups tip groups or the tip is below the root it is called an idol so we now have defined dihedral and also we twist okay I think we'll stop today what we have done essentially is we have defined certain important components or important parameters as far as aircraft is concerned which will be subsequently used for aircraft aerodynamics and which of course as a student in aerodynamics you should know in the beginning before you start your aerodynamics you

so welcome to introduction to aerodynamics this is an introductory course on aerodynamics the subject matter of aerodynamics is finding the or determining the forces and moments that acts on any body that moves through a feed in our case we are mostly interested in air but the basic principles are same irrespective of what fluid it is considering the body as an aircraft see one aircraft moves through a body it experiences certain force as you know that aircraft exerts forces on the air and air are in turn exerts forces on it and these force and moments and estimation of their contribution to the motion that is what is the subject matter of aerodynamics since these force and moments comes because of the pressure and viscous stress that is develops on the surface of the aircraft so aerodynamics try to determine these pressure and viscous stresses on the surface and of course these pressure and viscous stresses are dependent on the overall flow so you can say that aerodynamics is the study of the flow about any body that is immersed in a fluid and moving through it we are mostly interested in the body of aircraft and if we consider aircraft let&#39;s say what are the forces that acts on an aircraft we know that there is a by own sea force but usually the buoyancy force is so small that it is hardly considerable when compared to the total weight of the aircraft and we can neglect it for further motion now aircraft considering the simplest possible flight which is that aircraft flying in a straight level flight that it is going straight and keeping its altitude more or less fixed under this condition you know that the forces need a balance the weight force needs to be balanced by some pose similarly the engine thrust is also balanced by some other forces and these forces are in this configuration of flight are known as the lift and drag force that is on the aircraft is in a steady level flight it is balanced by the lift force and the thrust is balanced by a drag force both of these forces are in aerodynamic nature that is they comes because of the relative motion of the aircraft and the air or the fluid now if there is any disturbance in the flight of course the moment develops and the configuration of the aircraft changes the force coming from the pressure distribution and viscous stress distribution and they are distributed over the entire surface of the aircraft okay it&#39;s not necessarily a trap it can be any body which is immersed in fluid now as you know that a distributed force can be represented by a system of force and moments same thing can be done here also and these force and moments that can be resolved in any three mutual orthogonal direction if we consider these three mutual orthogonal direction are like this but if you remember this direction the let us call it X axis the x axis is along the relative wind it is along the relative wind that means it is along the direction of the relative velocity between the body and the feed is neither horizontal nor vertical or anything it is along the direction of relative velocity between the body and the fluid so as an example if we consider that an aircraft is moving in atmosphere which is at rest then the relative wind is simply the direction of or opposite of the direction of the aircraft speed so in that case the x axis is opposite to the direction of the aircraft velocity if an aircraft is flying through an atmosphere at rest the x axis is along the opposite of the direction of aircraft velocity or aircraft speed however in general we&#39;ll call it the direction of the relative wind the x axis is related in the direction relative to the wind and let us call at this stage the Jade axis which is up or but not vertical it is normal to of course the x axis so it is upward but it is not vertical since x axis is not hot horizontal the Jade axis is not vertical and the y axis is okay which is perpendicular to the plane formed by X and jet usually for an if we consider the body to be an aircraft we call it the direction to the right wing right side of the wing with respect to the pilot so the right side can be with respect to an observer the observer may be I found observer may be behind so of course the right side will change series right side with respect to the pilot usually that is called the starboard side these names came from shipping where they have the left side is usually called the port side as ships comes into a port its left side is usually faces the port towards the port so that left side is called the port side and the right side is called the starboard side and same nomenclature is used here in aircraft also so the right side of the aircraft is called the starboard side and the left side is called the port side so now the axis system that will that is usually followed in all aerodynamics you will study in other subjects the aircraft motion the dynamics of complete aircraft and in that context we will define various type of axis system but the axis system that is used in aircraft so the aerodynamics is like this the x-axis is along the relative wind jet axis is normal to x-axis upward positive and y-axis is normal to the plane of form by X and jet and to the starboard wing side is positive now if we resolve the force in these three direction in these three direction the component in the x direction is called the drag force so you see that the drag force is a component of the force along the relative guen direction the drag force is along the relative wind direction and again taking that example that aircraft moving through atmosphere at rest then it is opposite to the direction of aircraft speed the drag force is opposite to the direction of the velocity of the aircraft the force which is normal to this x-axis that is along that direction is called lift so lift force is normal to the relative wind it&#39;s not vertical lift force is not a vertical force it is normal to the relative wind and the force in the y-direction is called side force it is positive if it is towards the starboard if its reaction is towards the starboard it is positive the three moments the three moments about these three axis are called as pitching moment if it is about the y-axis the peak let&#39;s come from the moment about x-axis the moment about the x-axis is called rolling moment now what will this moment do as you can see that if an rollin moment acts on an aircraft it will try to bring one wing of the aircraft down with respect to the other wing one we will go up the other wing will come down that is what the rolling moment will do if a rolling moment acts on an aircraft its following will come downward the other room will go up if the starboard wing goes down the rolling moment is called positive similarly the moment about the y-axis that is an axis which is along the length of the wing or almost along the length of the wing a moment about that axis is called the pitching moment and what will be the action of this moment you can see that if there is a moment acting about this axis I the other nodes of the aircraft will go up or go down if the sense of the moment is such that the nose of the aircraft goes up then it is called a positive pitching moment similarly hearing moment a moment about the z-axis which can be called approximately vertical it is not the vertical direction but approximately vertical direction now a moment about it what will you do it will take the nodes to the left or right it will tend to move the nodes towards the left or towards the right if if it tends to move the nose towards the right that is towards the starboard side the young moment is taken as positive now so we have defined the three aerodynamic forces and aerodynamic moments all the forces and moments comes because of the relative fluid flow over the body so this is also another basic premises in aerodynamics that in aerodynamics we consider the body is at rest while the fluid is moving in the real world if you look to an aircraft it is the aircraft which is flying that Moscow is more or less at rest there might be a small wind which is say negligible as far as the speed is concerned is negligible to the speed of the aircraft while and aircraft flies at a speed of some 700 800 or 1000 kilometer per hour the wind is about some 4050 even less than that sometime 20 kilometer per hour so which is negligible so usually it is in the real life the aircraft moves that air is at waist that most fair is rate at waist in aerodynamics we consider it the other way it is always taken that the body is at rest and the fluid is moving through it that is you consider the relative velocity and all these forces this lift drag pitching moment going moment all comes because of these relative flow the relative velocity because of the flow field of course that is the subject matter of aerodynamics to analyze that flow field and to obtain these forces now think about an aircraft which is flying straight and level 100 flying straight and level of course no moment is acting no moment is acting and again as long as it flies straight and symmetric you see that the side forces or this Ewing and rolling moment they do not act the joining moment and side force rolling moment they come into picture only when there is an asymmetric flight if there is no asymmetric fight the forces or moments do not come into picture so during the flight time of an aircraft most of the time the aircraft is not experiencing any going moment or rolling moment neither any side force of course there are certain situation when all of these are acting or even these young moment rolling moment on side forces are acting but most of the time during its flight only lift and drag and possibly teaching moment acts now before we move to the real subject of aerodynamics lists give sudden important information as far as aircraft is concerned you know an aircraft consists of different components the most important components of an aircraft are it&#39;s useless the wings horizontal and vertical tails and engine these are the most important component of an aircraft the horizontal and vertical tail they are also like wings and so the most of the conventional aircrafts as you can say perhaps we can sketch that they look something like this this is what is the side view of an aircraft if you see it from side this is what it looks like a side view for this main body is called the fuelers or it houses all the important payloads if it is an commercial airliner this is where all the passengers will be this is the wing as it appears in a side view of course in a side view you will see only a cross-section of the wing this is called the horizontal tail plane of the aircraft here also you see only the cross-section and this is called the vertical tail and see there will be an engine usually attached to the wing so you can name it this you sorry the wing the horizontal tell and this is vertical tell this is what is the the plan of you here you have shown the wing as something like trapezoidal but that is not necessarily true that there we has to be travel the plan form the plan form can be of various shape it can be even a triangular what is called the delta wing and see we have shown here the leading edge this is called the leading edge and this is called the trailing edge so the leading edge of the wing we have shown here as a straight it is not necessary to to be straight it can be curved so this is our representative D of the aircraft or representative aircraft you can say a conventional aircraft there are many non conventional aircraft where you can clearly identify all these different components in such a manner now as far as the aerodynamics is concerned the most important component of the aircraft is the wing because these produces perhaps more than 95% of the total lift that the aircraft produces for a conventional aircraft almost the entire lift comes from these wings so this wing is the most important aerodynamic component tell is of course a small wing the horizontal tail vertical tail is a vertical owing we can say now we have seen this cross-section of the wing which are the special shape usually it is quite thin the thickness is of the order of say of course it is a variable it is not that for all aircraft the wing thickness is same the thickness is of the order of something like say 10% 12% of the call may be then less now we will define what is the score and certain important definition which are required in the later stages of aerodynamics that will come forward the shape that the wing takes in its platform in its plan view is called its plan form the shape that the wing takes in plan view is called its plan form so in this case the plan form is trapezoidal so horny call the plan form of a wing it simply means that how how does it looks horny take its plan view okay that is how you take its projection in plan then the distance between one wingtip to the other wing tip that is the distance from here to here the distance from here to here is called the wingspan distance from left wing tip to the right wing tip is called the wingspan in doing so you see that we are considering even that part of the figures the wing is connected to the feelers so in within the fuselage the wing is not there doing is not extended but while talking about the fun we talk about the entire wing tip to wing tip as if the wing is inside the fuselage also another very important quantity is the planform area as you have seen that the plant form is simply the view that the wing takes in its plan view so the area of that plant view is the wing area now then there is a question that how you take the plan view of the wing as you can say that in the plan the wing is up to this to the fuelers so this is the plan in this case the plan view is say a trapezoidal so the area of this trapezoidal this two trapezoid but it is not exactly so it has to be extended within the wing within the fuelers that means while finding the wing planform area the wings will be extended up to this and the area of these to fill these two trapezoids not only up to the fuelers but to the center of the fuelers extend the plant view or plant form to the center of the aircraft and then find its area that is what is the platform area square root of sorry square of span / transform area is called the aspect ratio of wing the aspect ratio of wing is so span distance from tip to tip there are common aerodynamic notation for these quantities the span is usually denoted by B the span is usually denoted by B more or less an Universal notation the planform area is denoted by the word letter s capital S the aspect ratio most often denoted by a joint a are in some cases you will find only a also but most often it is used as a joint AR and that is the notation we will also follow it is simply B Square by s or denoted by C it is distance from leading-edge two trailing edge now you can see that in general the score is then changing is not fixed quantity and there are various mean calls defined one is of course a geometric mean curve the other is called the aerodynamic mean curve how do you define these geometric mean code it is obviously quite the smallest is to represent semi span half of the span smaller is stands for B by two now the wing we have already talked about wing tip the wing at the junction or at the central axis as you said that if we extend the wing to the center of the aircraft then the chord length at that that is cod it is called the wing root coming back to the told figure the wing root here so this is root this is tip this is leading edge this is trailing edge there will be a difference in the cord length or the tip and core length at the root and their ratio is called the taper ratio tip cod2 root core the ratio tip cod2 root core is called the taper ratio okay forgot to tell aerodynamic mean code the aerodynamic mean code is defined as if the wing is shift backward with respect to that is from the root to tip if it goes backward with respect to the say the y-axis then the wing is called a shift back wing and the angle between the y-direction and the leading edge is called the surfed back angle again let us with respect to this figure itself if we have this is the direction of the y-axis then this angle is called feedback angle eventually what we defined is specifically it is called leading-edge feedback it is called leading-edge feedback though we have called it sieve back because the feedback may vary at different that is the leading edge may have a different sweep angle than the trailing edge the trailing edge sweep angle will not be same as the leading edge and also if we take any other line on the wing at certain fixed percentage of curve then the sweep angle of that line may be different or rather in general they are different let us say that we think about a mid Cod mid-quarter location that is at every section on the wing we will look at the mid Cod and then join it by a line then we get a midcourt line again let us take it one particular wing cross-section only let us consider and let us say this is the direction of Y axis so this is leading a shape similarly this will be trailing a shape usually denoted by this and similarly let us say we have midcourt line that is at every station we are locating this line is passing through the middle of the core at every station or say think about the 25% quarter line so each line edge all the lines have different ship trim back and as we mentioned that in many cases they are craft leading edge itself can be a curved line and if it so happens then you can see that the sweep even on a particular line shape changes they are called variable-sweep geometry if the leading edge is curve then the sweep angle changes along the leading edge itself so they are called variable shift between No we&#39;ll come to this the section of the wing the section of the wing is called an airfoil all British English was aerofoil so sometime we may call aerofoil and nowadays in the American English it has become airfoil so both will be used we cross-section geometry this is what is unusual shape of air fall if we join it from leading edge to trailing edge the line joining it is called its core the line joining the leading edge to trailing edge is called the core and at any particular corage location if we have the distance between the upper and lower surface is called its thickness this is all the upper surface of their fault and this will be calling the lower surface in aerodynamics of airfoil usually this point or the core intersects the nodes node of the airfoil is taken as the origin of the axis system and it is conventional conventional to take the x axis along the power the study of aerodynamics usually the leading edge sorry the coordinate origin is placed at the point where the core intersects the nodes that is here and the x axis is taken along the curve and of course the their axis is normal to the most important quantity in aerodynamics you are saying that is called an angle of attack angle of attack it is the angle between the relative wind and the chord line if we call this is the relative wind we will be denoting it by u infinity Y will come later infinity and this angle between this and this is all alpha and remember that the force lift force is normal to this u infinity and the drag force is along u infinity for a supersonic use often the leading edge of the airfoil is also pointed oil for subsonic use the leading edge is smooth and round but for supersonic huge often the leading edge is sharp now we have defined thickness and core in aircraft almost all length almost all length parameters are non dimensionalized with respect to curve often it is mean aerodynamic curve or mean geometric curve either of them so let us say that the thickness or all other parameters of an aircraft will always be expressed in terms of percentage curved air faults are usually designated by their thickness so hone it is called that an airfoil is 10 percent thick meaning the air fall has maximum thickness of 10 percent of its core that is if the power of the airfoil is say 1 meter then the maximum thickness of that air fall is 10 centimeters if we called our fall as 10 percent thickness if the maximum thickness as you can see that the thickness changes from leading edge to trailing edge at the trailing edge the thickness become practically zero and the maximum thickness occurs somewhere ahead of mid curve depending upon the type of airfoil it is a mid curve if the power is if the core does not intersect or does not divide the air fall into symmetric hub okay that is upper half and the lower hub are not symmetric with respect to the curve then the air fall is called a Campbell fall then their fall is called a camber airfoil if if it is symmetric that is if it is exactly at the middle of their fall then therefore is called symmetric so the air Falls can be either symmetric or asymmetric which is called camber cambered CA in b e ra d camber Converter for you it is not symmetric about the hole early now in such a case of course you can see that you can imagine or you can construct a line which is exactly at the center of therefore at each section at each station you can think about the thickness and then take the midpoint and join all the midpoint and you will get a line which is just at the middle of their fall within the middle of their form so that line is called the mean line or camel line that line if we join the 50% of the thickness line at each station and construct a line that line is called the mean line or camber line if the mean line is above the curve then the air fall is called positively camula cambered that is when the mean line is above the cowl it is positive number if the mean line is below the curve it is negative camber usually all practical aircrafts are positive camber something else we missed that is a diadem what is it I head out see how an aircraft has two wings on its two sides on the left-hand ride and think about that for each wing if we think about the cross section all the cross sections are an airfoil all the cross sections are an or fall so thinking about that wing over the semi span at each each station it has its own airfoil now the power of each of these airfoil caught up each of these our fall may not be in the same plane if they are not in the same plane sorry then the wing is called a twister giving a geometrically twisting wing on the car at each section is not on the same plane then the wing is called a twister living and in such a case you can see that the angle of attack at each cross section will also be different the angle of attack at each cross section will also be different however if the power on the same plane then the wing is called untwisted and in such a case if the if all their faults are same or false then the angle of attack at each section will also receive a wing or aircraft is called a having dihedral wing when the two wings are not on the same plane in in a front view with a dihedral wing it will look like this so this is called at Hydra level and this angle is called the dihedral angle similarly the wing is such that it&#39;s tip is drooped with respect to the root then it is called anhedral the the opposite call is called anhedral where the tepees groups tip groups or the tip is below the root it is called an idol so we now have defined dihedral and also we twist okay I think we&#39;ll stop today what we have done essentially is we have defined certain important components or important parameters as far as aircraft is concerned which will be subsequently used for aircraft aerodynamics and which of course as a student in aerodynamics you should know in the beginning before you start your aerodynamics you

Transcript for:Introduction to Aerodynamics

Transcript for:
Introduction to Aerodynamics