Comparison between CFD and Measurements for Real-gas Effects on Laminar Shockwave Boundary Layer Interaction, I.

Transcription

1 Comparison between CFD and Measurements for Real-gas Effects on Laminar Shockwave Boundary Layer Interaction, I. 20 June 2014 MacLean, Matthew Holden, Michael Dufrene, Aaron CUBRC, Inc.

2 New Test Cases for Hollow Cylinder Flare Model 2

3 New Test Cases for Double Cone Model 3

4 Comparisons to Previous Data Obtained over Double Cone Model from LENS-I Reflected Shock Tunnel 3 MJ/kg (2.5 km/s) Nitrogen 5 MJ/kg (3 km/s) Air 10 MJ/kg (4.5 km/s) Air 4

5 Test Conditions for Double Cone and Hollow Cylinder Flare Experiments Double Cone Hollow Cylinder Flare 5

6 Operation schematic of an Expansion Tunnel 1. Three tubes initially separated by diaphragms (test gas shown in center tube) DRIVER TEST GAS ACCELERATION GAS 2. Breaking the primary diaphragm transmits a shock into the test gas, increasing its pressure 3. When the shock reaches the secondary diaphragm, the higher pressure test gas breaks it and causes the test gas to expand into the acceleration tube 3. The expanding test gas cools and gains velocity while it drives a very strong shock through the acceleration gas ahead of it Freestream gas Shock-heated accelerator gas 5. Testing begins as soon as the test gas arrives at the test station and lasts until the unsteady expansion fan begins to alter the freestream state of the gas [ O(~1ms) ] Freestream gas 6

7 TIME (t) Wave Diagram of an Expansion Tunnel showing Propagation of Shocks, Expansions, and Contact Surfaces Test Time Limited by Two Factors: Head of unsteady expansion (reflected off primary contact) Tail of unsteady expansion unsteady expansion adds kinetic energy directly (U5 >> U2) peak temperature (2) 5 TEST TIME expansion wave contact surface shock 4 1 freestream (5) POSITION (x) DRIVER TEST GAS ACCELERATION GAS assume: P 4 >> P 1 >> P 10 7

8 Freestream Condition Calculation for LENS-XX CUBRC High Enthalpy Expansion Tunnel Analysis (CHEETAh) Code Numerically solves 1D primary and secondary wave systems (shown right) incorporating equilibrium chemistry, thermodynamics, ionization, etc. Makes use of measurable quantities like shock speed, Pitot pressure, static pressure, etc. to anchor the solution. Rapid, real-time solution of as-run freestream conditions available in less than 1 second. Primary Shock system Secondary Shock system 8

9 Development of Separated Region over Double Cone: Run 05 Arrival of initial gas marked approximately by time=0.0 Separation length estimated using distance from the corner forward to the point where heat flux sharply drops on the front cone (eyeballed). Accelerator gas pre-cursor time is shown in yellow, followed by establishing test gas shown in gray the accelerator gas partially develops the separated region. As pressure and heat flux rise post-test as shown in blue, separation point remains invariant for quite a while. 9

10 Development of Separated Region over Hollow Cylinder Flare: Run 04 Separation region size is approximately 2.5X the size observed on the double-cone; establishment timescale seems to increase correspondingly. In all cases, the hollow cylinder over-shoots (separated region gets too large) immediately after the contact surface arrives, and then shrinks back to its minimum observed size (recall the CFD solutions over-predict this). Post-test as pressure and heat flux rises on the model, separation region increases again (as Reynolds number increases) 10

11 Freestream Conditions Run # Total Enthalpy (MJ/kg) Mach Number Pitot Pressure (kpa) Unit Reynolds Number /10 6 (1/m) Velocity (km/s) Density (g/m 3 ) Temperature (K) Run # Total Enthalpy /10 6 (ft 2 /s 2 ) Mach Number Pitot Pressure (psia) Unit Reynolds Number /10 3 (1/ft) Velocity (kft/s) Density x10 6 (sl/ft 3 ) Temperature (R)

12 Run 01: [3.2 km/s, 0.5 g/m 3 ] 12

13 Run 02: [4.3 km/s, 1.0 g/m 3 ] 13

14 Run 03: [6.0 km/s, 0.5 g/m 3 ] 14

15 Run 04: [6.5 km/s, 1.0 g/m 3 ] 15

16 Run 05: [6.0 km/s, 1.1 g/m 3 ] 16

17 Run 06: [5.4 km/s, 2.1 g/m 3 ] 17

18 Reynolds Number Trend in Experimental Data 18

19 Velocity (Enthalpy) Trend in Experimental Data 19

20 Freestream Conditions Run # Total Enthalpy (MJ/kg) Mach Number Pitot Pressure (kpa) Unit Reynolds Number /10 6 (1/m) Velocity (km/s) Density (g/m 3 ) Temperature (K) Run # Total Enthalpy /10 6 (ft 2 /s 2 ) Mach Number Pitot Pressure (psia) Unit Reynolds Number /10 3 (1/ft) Velocity (kft/s) Density x10 6 (sl/ft 3 ) Temperature (R)

21 Run 01: [3.1 km/s, 0.6 g/m 3 ] 21

22 Run 02: [4.5 km/s, 0.5 g/m 3 ] 22

23 Run 03: [4.7 km/s, 1.8 g/m 3 ] 23

24 Run 04: [5.5 km/s, 2.2 g/m 3 ] 24

25 Run 05: [6.5 km/s, 0.9 g/m 3 ] 25

26 Reynolds Number Trend in Experimental Data 26

27 Double Cone Data Obtained in LENS-I vs LENS-XX LENS-I NOTE: Reynolds numbers are 5 MJ/kg (3 km/s) not the same between the 10 MJ/kg (4.5 km/s) two tunnels! LENS-XX 27

28 Conclusions Unique dataset of laminar shock/bl-interaction experiments available from LENS-XX from 3 to 6.5 km/s freestream velocity. Comparison between LENS-I and LENS-XX at 5 and 10 MJ/kg compares favorably. Comparisons with CFD to be made at end of session. 28

29 Comparison between CFD and Measurements for Real-gas Effects on Laminar Shockwave Boundary Layer Interaction, II. 20 June 2014 MacLean, Matthew Holden, Michael Dufrene, Aaron CUBRC, Inc.

30 Model Configurations 30

31 Freestream Conditions Run # Total Enthalpy (MJ/kg) Mach Number Pitot Pressure (kpa) Unit Reynolds Number /10 6 (1/m) Velocity (km/s) Density (g/m 3 ) Temperature (K) Run # Total Enthalpy /10 6 (ft 2 /s 2 ) Mach Number Pitot Pressure (psia) Unit Reynolds Number /10 3 (1/ft) Velocity (kft/s) Density x10 6 (sl/ft 3 ) Temperature (R)

32 Run 01: [3.2 km/s, 0.5 g/m 3 ] 32

33 Run 02: [4.3 km/s, 1.0 g/m 3 ] 33

34 Run 03: [6.0 km/s, 0.5 g/m 3 ] 34

35 Run 04: [6.5 km/s, 1.0 g/m 3 ] 35

36 Run 05: [6.0 km/s, 1.1 g/m 3 ] 36

37 Run 06: [5.4 km/s, 2.1 g/m 3 ] 37

38 Freestream Conditions Run # Total Enthalpy (MJ/kg) Mach Number Pitot Pressure (kpa) Unit Reynolds Number /10 6 (1/m) Velocity (km/s) Density (g/m 3 ) Temperature (K) Run # Total Enthalpy /10 6 (ft 2 /s 2 ) Mach Number Pitot Pressure (psia) Unit Reynolds Number /10 3 (1/ft) Velocity (kft/s) Density x10 6 (sl/ft 3 ) Temperature (R)

39 Run 01: [3.1 km/s, 0.6 g/m 3 ] 39

40 Run 01: [3.1 km/s, 0.6 g/m 3 ] 40

41 Run 02: [4.5 km/s, 0.5 g/m 3 ] 41

42 Run 02: [4.5 km/s, 0.5 g/m 3 ] 42

43 Run 03: [4.7 km/s, 1.8 g/m 3 ] 43

44 Run 03: [4.7 km/s, 1.8 g/m 3 ] 44

45 Run 04: [5.5 km/s, 2.2 g/m 3 ] 45

46 Run 04: [5.5 km/s, 2.2 g/m 3 ] 46

47 Run 05: [6.5 km/s, 0.9 g/m 3 ] 47

48 Run 05: [6.5 km/s, 0.9 g/m 3 ] 48

49 Conclusions Dataset of laminar shock/bl-interaction experiments available from LENS-XX from 3 to 6.5 km/s freestream velocity. In general, the CFD simulations are very consistent with each other except for specific instances shown during the presentation. In general, the CFD tends toward over-predicting separated region length on the hollow cylinder flare and under-predicting separated region length on the double cone. Data on the hollow cylinder flare in the attachment region shows consistently broader character than the CFD predicts reason unclear. 49