7. Consider a CFD simulation of air flow over a truck. The simulation was completed and below are the residual plot (Figure 9) and reported results (Figure 10 and Table 1). a) In the residual plot, find the criterion used in the residual error control and explain how to find it. (3 marks) b) In the residual plot, what is the actual residual error for the continuity equation? Draw an illustration line and provide an approximate value. (3 marks) c) Find the total drag force and total down force of the truck? (4 marks) d) If we know the drag forces at 79.8tN Truck front region (as shown in Figure 10): 79.81 N Window: 24.08 N Rear region: 47.05 N Is there another source of drag force on the truck body apart from the above three regions? Explain how to check. If yes, estimate the value and possible locations. (5 marks) Momentum and Mass Turbulence (KE) Variable Value 1.0e+00 1.0e-01 1.0e-02 1.0e-03 1.0e-04 1.0e-05 1.0e-06 0 10 10 20 30 Accumulated Time Step RMS P-Mass RMS U-Mom 40 50 RMS V-Mom RMS W-Mom