CFD Midterm Questions And Answers With Complete Solutions

"CFD" stands for ... correct answer: Computational Fluid Dynamics CFD and Computational Aerodynamics are different names for the same thing (True or False) correct answer: False The four primary steps in the CFD process are correct answer: geometry modeling, grid generation, flow solution, post processing CFD methods are also known as "low-fidelity methods" (True or False) correct answer: False FD techniques may only be used to model air as the working fluid (True or False) correct answer: False A properly written flow solver should be able to overcome input errors made by the user (True or False) correct answer: False When a flow solution is desired, CFD should not necessarily be the first method used (True or False) correct answer: True When performing any sort of computational analysis, a supercomputer should be the machine of choice (True or False) correct answer: False An example of a CFD post processor, and the one that we will be using, is correct answer: Fieldview Given proper input data (geometry and boundary/initial conditions), a good flow solver will provide an exact answer to the flow field (True or False) correct answer: False The set of equations governing a fluid flow situation include the conservation of correct answer: Mass, momentum, energy How many equations form the complete equation set for a 3D viscous flow solution? correct answer: 6 The order of the governing differential equation set for 3D viscous flow is correct answer: Second order The governing equation set for a 3D viscous solution is correct answer: nonlinear The dependent flow variables in the governing flow equations are correct answer: u, v, w, p (pressure), p (rho), T Similar to finding the solution to a set of coupled algebraic equations, in order to obtain the solution to a set of coupled differential equations, they must be placed into ___ form correct answer: Vector Which of the following is NOT one of the "types" of differential equations? correct answer: consistent For a Newtonian fluid, the shear stress is related directly to the velocity gradient through the correct answer: Dynamic viscosity In order to obtain the complete solution to the governing differential equations, it is necessary to apply boundary conditions and initial conditions in every case (True or False) correct answer: False The divergence form of the equations is required to capture discontinuities, such as shocks, in the flow field (True or False) correct answer: True An example of a 2D panel code is correct answer: XFOIL If an object is moving at less than sonic speed, it is impossible for there to be any supersonic flow anywhere on the object (True or False) correct answer: False To reduce the form drag on an object, it would be advantageous to have a turbulent boundary layer in the flow (True or False) correct answer: True The predecessor to NACA was NASA (True or False) correct answer: False "Panel methods" provide an exact solution to the governing equations of fluid motion in 3D (True or False) correct answer: False In most panel method computer codes, the level of accuracy is primarily determined by the correct answer: Number of panels used to approximate the geometry The following is a limitation of panel methods correct answer: They cannot be used to capture viscous effects Potential flow theory may be used to model any viscous flow situation (True or False) correct answer: False Panel methods may be used to simulate flows over curved surfaces, as well as flat surfaces (True or False) correct answer: True A turbulent boundary layer is always much thinner than a laminar boundary layer (True or False) correct answer: False The finite difference expression given below represents: correct answer: The second order central difference representation of the second derivative of u with respect to x In order to obtain the approximate solution to the governing differential equations of fluid motion, each term in the equations should be represented using some sort of finite difference expression. The resulting set of algebraic equations should then be solved using an appropriate solution technique (True or False) correct answer: True CFD solution techniques are only valid for subsonic flow (True or False) correct answer: False In the Finite Difference Method, the solution for the flow variables is assumed to exist correct answer: Only at the discrete points in the grid One method that may be used to generate finite difference expressions to represent derivatives is the Taylor Series Expansion (True or False) correct answer: True The finite difference expression given by represents correct answer: The first-order backward difference representation of the derivative of u with respect to x In the finite difference method, the "truncation error" represents correct answer: The order of the lowest-order term that was "dropped" from the infinite series Select all of the numerical solution techniques that are listed in the text correct answer: Finite Difference Methods, Finite Element Methods, Finite Volume Methods The "stability" of the solution method is not something that needs to be considered in a CFD analysis. All CFD solution techniques are inherently stable (True or False) correct answer: False A CFD solution is an exact solution to the governing equations of fluid motion (True or False) correct answer: False