Advancing Aerospace Research

Verification and validation for numerical methods with experimental results

Project Overview

Wedge-shaped protuberances appear in several forms on high speed vehicles, determined by mission requirements and design considerations. Control surfaces provide guidance, control and manoeuvrability. Sensors, probes and cameras are externally mounted to feed inputs to the control system. The design of such protuberances is crucial in the performance of space vehicles, especially during the re-entry phase and transatmospheric flights.

Project Summary

Experiments show that the attached flow has a dominant skin-friction drag component, while drag in separated flow primarily consists of pressure drag on the nose region. Drag coefficient approaches the limiting value with decreasing span (x/t > 8), while an increase in span approaches 2D compression corner results. Moreover effects due to strong viscous interactions occur typically over small lengths.

The addition of wedge-like fairings onto the side of missiles and space launch vehicles, to shield devices such as cameras and reaction jet nozzles, creates additional drag particularly when in supersonic and hypersonic freestream flow. An experimental and computational study was performed in order to obtain aerodynamic data on simple representative configurations in order to test the accuracy of simple theories for the drag increment due to these types of fairings.

A semi-empirical method to estimate drag on wedge-shaped projections is presented, which may be used by missile designers to provide predictions of the drag increment due to wedge-like fairings. The method is shown to be valid where the wedge width is much smaller than body diameter, and across the Mach number range 4 – 8.2, but is likely to be valid for higher Mach numbers.

Drag in Hypersonic Flow

Applied Aerodynamics Research

Sep 2012 — Oct 2013

While drag prediction is based on a simple model, presence of complex flow interactions account for local determination of hotspots. Locations and strengths of lateral vortices and their interaction with the bow shock are detailed in results from numerical simulation. A number of primary and secondary vortices interact with each other along the sidewalls. Incoming flow separates upstream of the wedge nose due to flow instabilities, resulting in separation and reattachment, and the increase in pressure drag that comes along with it. While flows with greater inertial effects are found to have little stabilizing effect on the state of the incoming boundary layer.