# Aerodynamics Questions and Answers – General Three Dimensional Flows-Panel Techniques

This set of Aerodynamics Multiple Choice Questions & Answers (MCQs) focuses on “General Three Dimensional Flows-Panel Techniques”.

1. Which of these flows is numerically computed using panel method technique?
a) Compressible flow
b) Incompressible flow
c) Anelastic flow
d) Pseudo-incompressible flow

Explanation: Panel method is a technique that is used to numerically compute the inviscid, incompressible flow around any arbitrary body. The panel method incorporates laying panels of source/doublet/votices distribution over the body to obtain the aerodynamic properties.

2. Which approximations are made in case of panel method in case of subsonic problems?
a) Quadrilateral panels with constant source strength
b) Curved panels with constant source strength
c) Triangular panels with constant sink
d) Quadrilateral panels with constant sink

Explanation: In case of panel method, the entire body is approximated into several smaller quadrilateral panels having constant source strength. Although when the bodies get complex, higher order panel technique is used, which makes use of curved panels with variable source strengths.

3. In how many categories is the panel method grouped into?
a) 2
b) 3
c) 4
d) 6

Explanation: Panel method is generally divided into two categories-Surface panel method and mean-surface panel method. Surface panel method is more precise and accurate as the number of panels can be increased based on the complexity of the body.

4. State true or false. Mean-surface panel method is used in case of final design calculations to get accurate results.
a) True
b) False

Explanation: Mean-surface panel method places the panels in the interior side of the body. This results in less accurate results and is only used for approximation. Thus, this method is used for preliminary design instead of final design calculations.

5. Which of these panels is distributed over a non-lifting body to analyze three-dimensional flow?
a) Source panel
b) Sink panel
c) Vortex panel
d) Doublet panel

Explanation: In case of non-lifting bluff bodies, source panels are distributed to analyze the three-dimensional potential flow unlike distribution of both vortex and source panels in case of lifting bodies.
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6. Which of these panels is distributed over a lifting body to analyze three-dimensional flow?
a) Source panel
b) Sink panel
c) Vortex panel
d) Both source and vortex panels

Explanation: Unlike non-lifting bodies which makes use of only source panel, lifting doies have a distribution of both source and vortex panels to assess the three-dimensional potential flow.

7. State true or false. In order to check if the net sum of contribution from all the elements is zero, we need to select a point on a panel.
a) True
b) False

Explanation: In every panel, there is a point selected to analyze the flow field and to check if the net sum of contribution from other panel elements is zero. This point is known as the collocation point.

8. Which of these distributions is required in the wake region of the lifting body?
a) Source
b) Dipole
c) Sink
d) Doublet

Explanation: Lifting bodies have a trailing edge which leads to a wake region. In the wake region, there is formation of vortices due to the disturbances in the flow. In this region, a dipole or vorticity singularity is used.

9. Which panels are used in case of higher-order panel method?
b) Curved panels
c) Triangular panels
d) Square panels

Explanation: Higher-order panel method came into being when the panel method became computationally demanding for complex bodies. This method makes use of curved panels with variable source strength.

10. Who developed the panel method?
a) Hess and Smith
c) Theodore Von Karman
d) Karl Wieghardt

Explanation: In order to model the wing section there were two methods used-Conformal mapping and Airfoil Theory. But these methods were not general and hence basic panel method was developed by Hess and Smith at the Douglas Aircraft Co. in the late 1950s and early 1960s.

11. Which of these flows can be modelled by the panel method?
a) Compressible flow
b) Rotational flow
c) Incompressible flow
d) Supersonic flow

Explanation: Panel method is idea for design analysis for only incompressible flows. It lacks the ability to model viscous flow, rotational flow w and supersonic flow. A panel method performs best when modeling fully-attached, high-reynolds-number (> 105), subsonic (Mach number < 1) flow.

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