Resketch figure 115 and briefly describe critical Mach membe

Re-sketch figure 11.5 and briefly describe critical Mach member for in the flow around air fopil. For a print can an air foil, placed in a flow, write the equation that defines pressure coefficient, C_p 1s is dimensionless group C_p distribution on different airfoils. Also note this negative C_p, values going up. Write the equation to express C_p, in terms pf p, o_omega and M_infinity and C_+p in terms of C_po and M_infinity. It is understood that for for air flow M > 0.3 is not valid. For larger M values, ewe must use po/p = [1 + {gamma - 1/2}) M^2] write C_p in terms of M_infinity for flow around an airfoil. For air, use gamma = 1.4 and obtain a simplified version of the equation. Call at 11/59 A. Obtain a graph for C_p varies M_infinity. Study related contents in the text book, write the statement on the velocity and application of equation 11.59 and its graph. Consider your AE 344L experiment for NACA 0018 placed in a world tuned at a selected a with free stream velocity as measured. From the experiment, find q_infinity in the flow and minimum (p - p_infinity) can the airfoil. Calculate M_C, C_ and C_p0. Calculate C_ values for M_infinity - 0.4, 0.5, 0.6, 0.7 and 0.8. Provide a C_+p min and M_ graph for NASA 0018 can the same Cartesian frame that has the C_ Vs M graph for any airfoil (from Exercise 15). Determine critical C_p and critical Mach number for NACA 0018 and indicate a for which these values are estimated Propose another suitable a value for your next experiment planned to obtain C_p distribution on the airfoil. Re sketch Figure 1111 Studs related contents in the textbook Briefly describe c changes for the following M domains 0

Solution

As subsonic air flow over an airfoil, it acclerates, reaches a maximum speed and then decelerates toward the trailing edge.

since t0 = constant.

thus the MAch number of the flow increases and then decreases . the magnitude of this change depends on the airfoil shape and the angle of attack. thus it is evident that , as you increases M infinity , the highest local m on the surface may exceed 1 long, before M infinty reaches 1

the value of M infinty at which the highest M on the airfoil first reaches 1 is caled the critical Mach number Mcr.

Note: Mcr is value of freestream mach number

Mcr is less than 1 for anything with thickness at all.