Questions and Answers of Fundamentals Of Aerodynamics

How does the drag coefficient of an airfoil with ideal steady compressible flow vary with the Mach number and lift-drag ratio of the incoming flow?
For fluids with small viscosity coefficients, please explain why the viscous effect in the flow near the wall cannot be ignored.
Please explain the basic assumptions of the boundary layer approximation.
Write down the displacement thickness of the boundary layer, the thickness of the momentum loss, and the thickness of the energy loss. Explain the physical meaning.
The motion of the viscous fluid in the boundary layer is vortex motion. Please write down the relationship between wall vorticity and shear stress.
Please write down the vorticity diffusion equation in the boundary layer.
Please write down Prandtl’s boundary layer equation and explain how to calculate the pressure in the boundary layer.
Point out the physical meaning of the boundary layer similarity hypothesis.
Write the Karman momentum integral equation, and point out the condi-tions that need to be supplemented to solve the momentum integral equation.
Point out why the inverse pressure gradient and surface adhesion conditions are necessary conditions for boundary layer separation.
Why is the velocity distribution in the boundary layer near the object surface stable under the pressure gradient, and there is no velocity inflection point?
Why is the velocity distribution in the boundary layer near the object surface unstable under the reverse pressure gradient, and there is a velocity inflection point in the boundary layer?
Please indicate the conditions of the separation point in the boundary layer. Why does the resistance of the object flow around increase significantly after the boundary layer is separated?
Explain the basic measures for the proposed separation of the boundary layer.
Ideal incompressible potential flow, why the velocity potential function satisfies the Laplace equation.
For compressible potential flows, derive the differential equation that the velocity potential function satisfies.
Please explain the conditions for the ideal incompressible potential flow velocity potential function to satisfy the Laplace equation?
Please explain the conditions for the ideal incompressible potential flow function to satisfy the Laplace equation?
For incompressible plane flows, what is the relationship between flow function and vorticity?
For an ideal incompressible potential flow, prove that the streamline is orthogonal to the equipotential line.
Please give the formulation of the definite solution of the velocity potential function and the flow function for the potential flow problem around an object.
Please analyze the variation of pressure distribution along the surface in the flow around a blunt object to find the minimum pressure coefficient.
In the flow around the cylinder, please explain the variation of velocity and pressure along the cylinder surface from the front stagnation point to the rear stagnation point.
Let G(x, y) be the solution of the two-dimensional Laplace equation. Please prove that G(x, y) can represent the potential function or flow function of the two-dimensional inviscid and incompressible
Given the velocity potential ϕ = xy find the velocity component and the flow function, and draw the equipotential lines with ϕ being 1, 2, and
Prove that equipotential lines and streamlines are orthogonal to each other.
Under what circumstances can the viscosity of the fluid be reflected? From the perspective of the transport properties of fluid movement, what kind of transport characteristics does fluid viscosity
Please explain the physical meaning of Newton’s internal friction law? What is the physical mechanism of the dynamic viscosity coefficient?
Write down the deformation rate matrix of fluid clusters and its three invariants? Explain the physical meaning of divergence?
Write down the stress matrix of the fluid cluster and its three invariants? Explain the physical meaning of the nominal pressure acting on the viscous fluid clusters? In the movement of viscous
What are the three assumptions of Stokes regarding the generalized Newton’s internal friction law? And explain the physical meaning?
Write down the constitutive relationship of the incompressible viscous fluid micro-cluster motion. In the steady flow of a straight pipe with constant cross section, what is the constitutive
Write down the constitutive relationship of the three normal stresses in the steady flow of a shrinking pipe?
Write down the component expressions of the differential equations of motion of incompressible viscous fluids (Navier–Stokes equations)? Vector form? And the physical meaning of each item?
Why is the motion of viscous fluid generally vortex motion? For the motion of incompressible viscous fluid, where does the vortex mainly occur under the condition of mass force advantage? why?
Please explain that the flow field induced by an infinitely long rotating cylinder is viscous fluid motion, but non-rotating motion. That is, viscous potential flow?
Write the vorticity transport equation for the motion of incompressible viscous fluid, and point out the physical meaning of each item?
Write down the Gromic-Lamb type differential equation of motion for the incompressible viscous fluid, and explain the physical meaning of each item?
Under the action of gravity, for the Bernoulli equation of the N–S equa-tions of incompressible fluid motion along streamlines, explain the physical meaning of the Bernoulli integral, and explain
Explain whether the statement “Water always flows from a high place to a low place” is correct and why? If it is not correct, please give the correct statement?
Compared with ideal fluid motion, what are the main characteristics of viscous fluid motion?
Why do we say that viscosity and inverse pressure gradient are necessary conditions for boundary layer separation?
The adhesion condition of the object surface is the difference between viscous fluid turbulence and ideal fluid turbulence? Please explain the phys-ical reason for the resistance caused by the
Please indicate the main measures to reduce the resistance of low-speed objects moving around the flow?
In the case of the same Reynolds number try to find the ratio of frictional resistance when water at 20 °C and air at 30 °C flow parallel through a long plate. Rel,
The sound velocity a in water is related to the volume modulus K and density ρ. Use the Rayleigh method to derive the sound velocity expression.
Why did double-wing and triple-wing aircraft appear in the early days, but they are all gone today. Explain the main measures to increase the lift of the aircraft.
Qualitatively explain the reasons for the difference in the aerodynamic force of the flat plate, curved plate, and airfoil.
If the landing gear of the aircraft is not retracted, please explain how it affects the flight performance of the aircraft.
When an airplane is in flight, the balance requires that the total torque around the center of gravity of the airplane is zero. If the torque is unbalanced, what parts of the airplane are used to
Please give the dimension and unit of force, moment, and acceleration.
What is the relative principle of flight? The difference between ground speed and airspeed?
What is the difference in aerodynamics between flying upwind and flying downwind?
What is the scientific idea of aerodynamics of British physicist George Kelly?
Explain the velocities of the upper and lower wing surfaces in the airfoil flow, and indicate the force characteristics of the wing surfaces.
Explain the theorem (magnitude and direction of lift) of Russian physicist Joukowski.
In a straight and uniform flow, the lift of the cylinder is determined by the rotation speed of the cylinder. For a non-rotating wing, what can be used to change the lift?
During the flight of an airplane, the thrust and drag balance are generated by the engine. With what force and drag balance do birds fly?
Why is the fuselage of an airplane slender, and the slenderness ratio of an airplane generally taken? (The ratio of the length of the fuselage to the maximum diameter.)
Why does a fixed-wing aircraft roll during take-off, and explain the main factors affecting the take-off speed of the aircraft?
What is the main function of the winglet? Briefly describe the principle of pneumatics.
Briefly describe the reasons for the use of lift-increasing devices on the aircraft.
The Stokes–Oseen formula for the resistance on the sphere at low-speed V iswhere D = sphere diameter, μ = viscosity, ρ = density. Prove that the dimensions of both sides of the formula equal sign
It is proved that the dimensions are the same, and the volume flow Q through the orifice with diameter D satisfies the following formula, and the hole is located on the side of h below the liquid
Prove that the dimensions of the boundary layer x-momentum equation are consistent.Among them, u and v are the velocity components of the fluid particle move-ment, f x is the mass force per unit
What is the fluid continuum hypothesis?
How to describe the fluid state from a microscopic view? How to describe the fluid state from a macroscopic view?
Why can the Knudsen number be used to characterize the continuity of the fluid? Combining the standard atmosphere table, please indicate the height above which the continuum hypothesis is not
What is the fluidity of a fluid? Please explain the fluidity of the fluid from the microscopic view.
For air and water, if the volume is compressed by 1%, what is the increase in pressure?
What is the viscosity of the fluid? Why is the viscous shear stress in the fluid proportional to the rate of shear deformation, but not the amount of shear deformation?
Please explain the relationship between shear stress and deformation rate of Bingham fluid, pseudo-plastic fluid, swelling fluid, and Newton fluid.
Given that the barometer reads 2.5 atmospheres at a certain point, what is the relative pressure and the absolute pressure at that point?
What is the isotropy of static pressure at any point in a static fluid?
The distance between one plate and the other fixed plate is 0.5 mm. The space between the two plates is filled with liquid. The upper plate moves at a speed of 0.25 m/s under the force of 2 N per
In order to conduct insulation treatment, the wire is pulled through the middle of the mold filled with insulation coating. The diameter of the wire is known to be 0.8 mm and the viscosity of the
The two parallel disks have a diameter of D, the distance between them is h, the lower disk is fixed, the upper disk rotates at a uniform angular velocity ω, and there is a liquid with a viscosity
The upper and lower parallel disks have a diameter of d, the distance between the two disks is δ, and the dynamic viscosity of the liquid in the gap is μ.Ifthe lower disk is fixed and the upper
Assuming that the density of the atmosphere is a constant of 1.225 kg/m3, what is the upper bound of the atmosphere in m? (Assume that the pressure at sea level is the same as the international
A vertical clean glass manometer tube has an inside diameter of 1 mm. When pressure is applied, the water at 20 °C rises to a height of 25 cm. After correcting the surface tension, estimate the
The compressor compresses the air, the absolute pressure increases from 9.8067 × 104 Pa to 5.8840 × 105 Pa, and the temperature increases from 20 to 78 °C, how much is the air volume reduced?
An open glass tube with an inner diameter of 10 mm is inserted into water with a temperature of 20 °C, and the known contact angle θ = 10° between water and glass. Try to calculate the height of
A closed container contains 1.5 m of oil, 1 m of water, 20 cm of mercury, and a top air space, all of which are in 20 °C. If p Subscript b o t m Baseline equals 60 k upper P ap Subscript b o t m
The design height of an engine is 1000 m; try to find the atmospheric pressure density and temperature at this height, and compare them with the parameters given on the international standard
In the figure, sensor A reading is 1.5 kPa. All the liquids are at 20 °C. Determine the liquid level height Z(m) of the open manometer tubes B and C. 2 m Air 1.5 m Gasoline B C Im Glycerin 2-0
The volume of a gas storage tank is 6 m3, which stores 48.1 kg of air. Try to determine the density of the air in the air storage tank.
As shown in the figure, it is a water container with first-order acceleration moving downward. The water depth h = 2 m and the acceleration A = 4.9 m/s2. Try to calculate (1) the absolute static
The reading of the barometer on a certain day is 101.672 kPa. Try to calculate the force in N per 1 m2 of the atmospheric pressure.
The volume of a gas tank is 27.1 m3, stored with compressed air. Given that the temperature of the air in the tank is 303 K and the pressure is 127.825 kPa, what is the mass of the compressed air in
Use a metal tank with a volume of 1000 m3 for a water pressure test. First, fill the container with water with a pressure of 1.013 × 10°Pa, and then pressurize the water to increase the pressure in
Assuming that the temperature of the atmosphere is a constant of 288.15 K, try to calculate the pressure at 5000 m altitude. Please compare the pressure value with the corresponding value of the
Explain the physical nature of the Lagrangian method for describing the motion of a fluid particle?
Explain the physical nature of Euler’s method for describing the motion of fluid particles?
Try to explain the relationship between Lagrange variables a, b,c, t and Euler variables x, y, z, t.
In The Lagrange method, the pressure of the particle is p (a,b, c, t). Please explain the physical meaning of this expression?
Explain the physical meaning of the components of acceleration in Euler’s method? For steady flow, why can’t we say that the acceleration is zero?
What are the physical meanings of trace and streamline lines of fluid parti-cles? At what point do they overlap? For unsteady flows, why are they generally not coincident?
Explain the physical meaning of heat conduction and heat convection by using the matter derivative of temperature.
What are the basic motion forms of fluid particles? What are the basic modes of motion of fluid elements? Write the velocity expression (translational velocity, rotational velocity, angular
What are the similarities and differences between the rotation motion of micro fluid elements and the rotation motion of rigid bodies?

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