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HW 8 - t W a ifiifl'“’ ‘7 Homework 9 Shock...

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Unformatted text preview: t; W a ifiifl . '“’ ‘7' Homework 9: Shock / Expansion Theory Handed out Due Note: This assignment is worth 2 homework grades 1. For a given Prandtl—Meyer expansion, the upstream Mach number is 3 and the pressure ratio across the wave is 0.4. Calculate the angles of the forward and rearward Mach lines of the expansion fan. relative to the free—stream direction. 2. Consider a supersonic: flow with an upstream Mach number of 4 and a pressure of 1 atm. This flow is first expanded around a corner with 8 x 15 deg, and is then compressed through a corner with an equal angle so that it is returned to its original upstream direction. Calculate the Mach number and pressure downstream of the compression corner. 3. A supersonic get exits from a nozzle with an exit—to—throat area ratio of 3.0 into a region Where the back pressure is 0.?98 X 105 Pa. The reservoir pressure is 10 X 105 Pa, and the nozzle is overwexpanded. Given the sketch shown below, find the angles of the slip line :9 and 6 and the Mach numbers and pressures in regions (2M3)1 and nil W. PE) 3»; E. W a- 4. (Sampie Test Problem) Mach 4 air flows over the airfoil shown below. a. Sketch and label the wave patterns present in this flow h. Determine expressions for the lift and drag coefficients in terms of the pressure coefficients in regions 1,2, and 3 and the geometry. c. Calculate the pressure coefficients in each region, using shock-expansion theory. d. Using your resuits from and (o), calculate the lift and drag coefficients. 9 O 0.! Heme—Lt ~———e—--— ( I “1 / ’1‘: 5. (Sample Test Problem) The flow in the exit plane of a GE) nozzle merges with another 1 flow outside the nozzle. The two flowfields are separated by a slip Zine inclined 10 deg. upward, as shown. The nozzle has a reservoir pressure of 5 atm and an exit—to—throat area ratio of 25. The Mach number of the outside flowfield is 3.0 upstream of the lip of the nozzle. If the flow in the divergent section of the nozzle is supersonic and isentropic. a. Sketch the wave interactions that wiil occur in this flow, inciuding those downstream of point A. b. Caicuiate the Mach number and pressure at the exit plane of the nozzle. c. Calculate the pressures on both sides of the shp line (before point A) and aiso the pressure of the flow outside and upstream of the nozzle lip. M:2.CD A nun/Q10. 1’ m—s‘v ha 5. (Computer Problem) Consider Mach 3 flow past a double wedge geometry, as discussed in class. Modify your computer codes to calculate the angle that the slip line makes With the X axis and the pressures in Regions 4 and 5. Consider two cases, with each having 91 = 12 degrees and 92 m 15 degrees, but with the first case assuming that the coalesced shock is a weak obiique shock and the second assuming that it is a strong oblique shock. You may wish to verify whether the additional wave generated is a compression wave or an expansion wave before proceeding. Use the attached pieces of code to get a Mach number, given the Prandtl-Meyer function, for the case where an expansion fan is present. Turn in a copy of your code as weh as output tabulating your Merit function versus number of iterations for both cases. £95651 5- 37mph at / Co [\3 function rpm(xx) mm__-__%m____W____mMmmMwfl____________MW__WWWW____~___ this function inverts the PMM function to get the Mach number. A fiinitemdifference Newton method is used. This routine is accessed from the main program' by a statement such as xmach = rpm(xnu) where_xnu is the prandtl—meyer function (in RADIANS) and xmach is the returned Mach number W 00000000000000?) rpm 2 1.05 dxm = 0.00; do i=1,35 fx = pm(rpm)—XX if(i .eq. 1) fXO : fx if(abs(fx/fx0) .le. le~6) goto 998 dfxdx : (pm(rpm+dxm) — pm(rpm))/dxm rpm 2 rpm _ fx/dfxdx enddo write(6,*) ’convergence not reached“ ‘998 continue return end function pm(xx) __wmmmm___n__mWW___ia______mw____________~._______~.____mmfi this function computes the Prandtl—Meyer function given the Mach number XX. The P—M function is in RADIANS ——.~wmwm___flmwm_~___mmmmmmwm—___M___fl_fl—__H_ OODOOO pm 2 sqrt(2.4/O-4)*atan(5qrt(0.4*(xx*xx—l.)/2.4)) c — atan(sqrt(XX*XX—1.M return end ...
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HW 8 - t W a ifiifl'“’ ‘7 Homework 9 Shock...

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