Viscous Aerodynamic Shape Optimization with Installed Propulsion Effects

Abstract

Aerodynamic shape optimization is demonstrated to tailor the under-track pressure signature of a conceptual low-boom supersonic aircraft. Primarily, the optimization matches the near-field pressure disturbances induced by propulsion integration effects to a prescribed low-boom target. For computational efficiency, gradient-based optimization is used and coupled to the discrete adjoint formulation of the Reynolds-averaged Navier Stokes equations. The engine outer nacelle, nozzle, and vertical tail fairing are axi-symmetrically parameterized, while the horizontal tail is shaped using a wing-based parameterization. Overall, 48 design variables are coupled to the geometry and used to deform the outer mold line. During the design process, an inequality drag constraint is enforced to avoid major compromise in aerodynamic performance. Linear elastic mesh morphing is used to deform the volume grid between design iterations. The optimization is performed at Mach 1.6 cruise, assuming standard day altitude conditions at 51,707-ft. To reduce uncertainty, a coupled thermodynamic engine cycle model is employed that captures installed inlet performance effects on engine operation.

Supersonic Engine Inlet Tone Noise Radiation

“…The axisymmetric spike inlet geometry was supplied by the authors of [2] for use in the present study. This geometry features an auxiliary inlet but no struts supporting the center body.…”

“…This physical size was chosen to match the annular outer diameter of an existing ultrasonic fan noise simulator, which will be described in Section 3. This gives a scale factor of 11 for the LM1044 vehicle with its 1650 mm (65 inch) fan diameter and a scale factor of 6 for the 890 mm (35 inch) F404 engine fan used in [2]. Frequencies of interest will scale linearly, so to consider a tone of 2500 Hz full scale, model scale simulations would be at frequencies of 15 kHz to match the scale factor of 6 or 27.5 kHz for the scale factor of 11.…”

“…A render of the LM1044 showing the engine inlets in cruise configuration is given in Figure 1. A study led by NASA Glenn Research Center [2] considered the Low-Boom Flight Demonstrator concept geometry. Compared to the LM1044, this aircraft is a single occupant, single-engine design with a Mach 1.6 flight speed.…”

Multipoint Variable Cycle Engine Design Using Gradient-Based Optimization

“…We can use numerical optimization to find the best performance when varying the physical and operational variables. Engine optimization has been used in a variety of contexts, including propulsion-airframe integration [10,11], multidisciplinary design optimization (MDO) of an aircraft including its heat loads [12], or for boundary layer ingestion [13]. The large design space introduced by the VCE technology necessitates gradient-based optimization.…”

“…A cutout view of a representative engine with the IGV and VABI controls highlighted. Adapated from Heath et al[10].…”