Fully anisotropic goal-oriented mesh adaptation for 3D steady Euler equations

A summary is provided for the Second AIAA Sonic Boom Workshop held on January 8–9, 2017, in conjunction with AIAA SciTech 2017. The workshop used four models of increasing complexity: an axisymmetr...

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Nearfield Summary and Statistical Analysis of the Second AIAA Sonic Boom Prediction Workshop

Review and prospect of supersonic business jet design

Marketing surveys of traditional business aircraft operators have shown that there is significant interest customer interest in the development of a supersonic business jet. One requirement for such an aircraft is that it be capable of unrestricted supersonic flight over land. This requirement has focused considerable attention on sonic boom minimization for a class of 100,000 pound, Mach 1.6 to 2.0 cruise airplanes. Configuring the design with sufficient low boom characteristics while at the same time including enough cabin volume has proven difficult. Gulfstream has developed a Quiet Spike concept that significantly improves the sonic boom signature while at the same time allowing for additional fuselage volume. The multi stage extendable nose spike projects out of, and retracts into, the forward fuselage of the airplane. Wind tunnel tests of supersonic equivalent area distributions have validated the near field aerodynamics of the spike concept. CFD analysis of a wing/body configured with a multi stage spike have extended the analysis beyond idealized equivalent area distributions and shown a great potential for tailoring the shape of the sonic boom ground signature while simultaneously allowing greater flexibility in the fuselage design.

Improved Sonic Boom Minimization with Extendable Nose Spike

This paper addresses classical issues that arise when applying anisotropic mesh adaptation to real-life 3D problems as the loss of anisotropy or the necessity to truncate the minimal size when discontinuities are present in the solution. These problematics are due to the complex interaction between the components involved in the adaptive loop: the flow solver, the error estimate and the mesh generator. A solution based on a new continuous mesh framework is proposed to overcome these issues. We show that using this strategy allows an optimal level of anisotropy to be reached and thus enjoy the full benefit of unstructured anisotropic mesh adaptation: optimal distribution of the degrees of freedom, improvement of the ratio accuracy with respect to cpu time, ...

Optimal 3D Highly Anisotropic Mesh Adaptation Based on the Continuous Mesh Framework

An alternate approach has been identified for defining supersonic inlet compression surface geometry, the use of which increases the design latitude for lofting the inlet cowling region while permitting control over other key inlet design variables. Through this approach, a novel inlet design space is analytically shown to significantly improve supersonic aircraft performance and reduce sonic boom overpressure compared to high-speed inlets designed using traditional methods and constraints. Installed specific fuel consumption improvements of up to 11 percent and sonic boom overpressure reductions of 16 percent were observed for a podded axisymmetric external compression inlet designed for Mach 1.8 cruise. A theoretical discussion and physical description of the alternate inlet design concept is provided along with a summary of the analysis methodology used to judge the concept’s merit against conventional configurations. Inlet performance metrics, presented as a function of key design variables, are compared; and CFD solutions of the compression and diffusion flow environment are included. Drag characteristics at off-design Mach number are also presented. An extended range, low sonic boom vehicle concept is used as an aircraft study platform for which installed CFD-based drag and sonic boom comparisons are made.

Supersonic Inlet Shaping for Dramatic Reductions in Drag and Sonic Boom Strength

The Gulfstream Quiet Spike is a telescoping forward fuselage extension that alters the bow shock of the classic N-wave pressure signature generated by aircraft traveling at supersonic speeds. The bow shock is broken up into sequence of weak shocks that propagate parallel to each other without coalescing. The resulting rise time to peak overpressure in the ground signature is increased from two or three milliseconds to thirty or forty milliseconds, significantly reducing the loudness. The development history of the Quiet Spike concept is traced from initial conception up to the design of a flight test configuration. Early aerodynamic and structural tests matured the concept from one viewed with skepticism to one deemed possible. These tests and the subsequent development of an aerodynamic configuration that could be installed on an F-15B test aircraft are summarized and the objectives of the flight test program are discussed.

Development of the Gulfstream Quiet Spike TM for Sonic Boom Minimization

Method and arrangement for reducing the effects of a sonic boom created by an aerospace vehicle when said vehicle is flown at supersonic speed. The method includes providing the aerospace vehicle with a first spike extending from the nose thereof substantially in the direction of normal flight of the aerospace vehicle, the first spike having a second section aft of a first section that is aft of a leading end portion, the first and second sections having a second transition region therebetween and each of the sections having different cross-sectional areas, the leading end portion of the first spike tapering toward a predetermined cross-section with a first transition region between the predetermined cross-section and the first section. The first transition region is configured so as to reduce the coalescence of shock waves produced by the first spike during normal supersonic flight of the aerospace vehicle. A spike may also be included that extends from the tail of the aerospace vehicle to reduce the coalescence of shock waves produced by the spike during normal supersonic flight of the aerospace vehicle.

Supersonic Aircraft with Spike for Controlling and Reducing Sonic Boom

An alternative inlet design method employing isentropic relaxed compression has been developed by Gulfstream Aerospace Corporation for improving net propulsion system performance and reducing sonic boom strength. To substantiate results from prior analytical studies and to provide an experimental database for subsequent research, a wind tunnel test was conducted using a family of subscale axisymmetric relaxed compression inlet models designed for an incoming flow speed of Mach 1.97. All tests were performed in the 1 ft by 1 ft supersonic wind tunnel at NASA Glenn Research Center. Focusing on internal flow characteristics, a large database comprising nearly 1500 test runs was acquired, covering a range of subsonic diffuser Mach numbers, diffuser lengths, mass flow rates, and angles-of-attack. Differences in flow properties between inlet models were surprisingly modest despite significant changes in hardware geometry. Strut effects were noteworthy for all model designs. Comparisons with CFD proved the analytical methodology to be reliable for this application. The large experimental database will be used for additional analytical methodology development, design work, test planning at larger scale, and the development of non-bleed surface treatment concepts for boundary layer control.

Donald C. Howe

Papers

Improved Sonic Boom Minimization with Extendable Nose Spike

Supersonic Inlet Shaping for Dramatic Reductions in Drag and Sonic Boom Strength

Development of the Gulfstream Quiet Spike TM for Sonic Boom Minimization

Supersonic Aircraft with Spike for Controlling and Reducing Sonic Boom

Wind Tunnel Testing of an Axisymmetric Isentropic Relaxed External Compression Inlet at Mach 1.97 Design Speed