Transition Analysis for the HIFiRE-5 Vehicle

Abstract

The Hypersonic International Flight Research and Experimentation (HIFiRE) 5 flight experiment by Air Force Research Laboratories and Australian Defense Science and Technology Organization is designed to provide in-flight boundary-layer transition data for a canonical 3D configuration at hypersonic Mach numbers. This paper outlines the progress, to date, on boundary layer stability analysis for the HIFiRE-5 flight configuration, as well as for selected test conditions from the wind tunnel experiments supporting the flight test. At flow conditions corresponding to the end of the test window, rather large values of linear amplification factor are predicted for both second mode (N>40) and crossflow (N>20) instabilities, strongly supporting the feasibility of first in-flight measurements of natural transition on a fully three-dimensional hypersonic configuration. Additional results highlight the rich mixture of instability mechanisms relevant to a large segment of the flight trajectory, as well as the effects of angle of attack and yaw angle on the predicted transition fronts for ground facility experiments at Mach 6. Backgroundue to its influence on surface heat transfer, skin-friction drag, and flow-separation characteristics, prediction of boundary layer transition constitutes an important aspect of hypersonic vehicle design. Laminar to turbulent transition over realistic vehicle surfaces is often caused by surface roughness of sufficiently large magnitude. However, when the surface is relatively smooth, the transition process is initiated by linear instabilities of the laminar boundary layer. Typically, the second (or Mack) mode instability dominates transition in 2D and axisymmetric boundary layers with hypersonic edge Mach numbers, although centrifugal (i.e., Gortler) instabilities may also come into play when the surface has concave curvature along the streamwise direction. Three-dimensional boundary layers involve the additional mechanisms of stationary and traveling modes of crossflow instability and, depending on the geometric configuration, may include the attachment line instability as well [1].Regardless of the speed regime, linear stability correlations have been quite successful in predicting the onset of transition when a single instability mechanism dominates the transition process [2]. Mixed mode transition has been more challenging to predict because of possible nonlinear interactions between the relevant modes of instability. To account for the effect of such interactions, an ad hoc composite metric based on the linear amplification factors for the different instability mechanisms has sometimes been used for transition correlation (see, for instance, [3]). Recent work on crossflow instability in low-speed boundary layers [4] has exposed additional shortcomings in applying purely linear predictive models to crossflow dominated transition in 3D boundary layers.The simplest canonical configuration that includes the necessary elements for studying both mixed mode transition and crossflow evolu...

HIFiRE-1 and HIFiRE-5 Test Results

“…During descent, latest (highest Reynolds number) leading edge transition occurred when the diameter Reynolds number at the most upstream joint was 1. The minor axis (centerline) transitioned at a lower Reynolds number than the leading edge, which is consistent with prior CFD 69,70 and wind tunnel measurements 53,65 at hypersonic conditions that indicated that the centerline is more unstable and prone to lower Reynolds number transition. Centerline transition also showed a more gradual progression over time than the leading edge transition.…”

“…This behavior indicates that the acreage transition appears to have been uninfluenced by tripped transition at the leading edge. The transition pattern agrees qualitatively with patterns observed in hypersonic wind tunnel experiments and computations 69,70 for hypersonic flight Mach numbers, with centerline transition occurring earlier than leading edge transition, due to the more unstable centerline boundary layer.…”

“…For reference, an N-factor contour plot (reproduced from Ref. 69, with sensor locations and notation added), for traveling crossflow at Re=9.8×10…”

Transition Analysis for the Mars Science Laboratory Entry Vehicle

“…The results suggest that a transition N value of 4 and 6 for stationary and traveling crossflow modes, respectively, appears to give reasonable transition estimates off the leeward meridian of symmetry. These results are in line with a slender cone type configuration investigated within the same wind tunnel [15]. This paper provides preliminary analyses for transition over the wind tunnel models relevant to the MSL flight vehicle.…”

“…Each streamline shown in the figure starts at the onset of instability and extends to the location where a prescribed N value (4 for stationary crossflow and 6 for traveling crossflow instability modes) has been reached. The selection of 4 and 6 is based on the correlated stationary and traveling crossflow transition N-factor of the HIFiRE-5 vehicle model tested in the same NASA Langley wind tunnel [15]. The predicted transition fronts agree reasonably well with the off-axis transition patterns shown in Fig.…”