• Dr. Pradeep Raj
  • Independent Consultant
  • 310 ICTAS
  • 12:00 noon
  • Faculty Host: Dr. Rakesh Kapania

Computational Fluid Dynamics (CFD) capabilities for flow analysis have evolved from simplified geometry, simplified physics models of the late sixties and early seventies to complex geometry, sophisticated physics models used routinely today. In the early years, some experts unrealistically expected CFD to displace and supplant wind tunnels for producing aerodynamic data for aircraft design—characterized by this author as irrational exuberance. However, even after more than three decades of dramatic advancements, the full potential benefits of CFD elude us; it continues to serve as an able complement to wind tunnels. Our inability to produce credible computational predictions is the primary cause of this predicament—a sobering reality indeed. Going forward, it is essential that we focus our energies on correcting this situation because ability to produce credible data using CFD is the cornerstone of a promising strategy for successfully tackling the affordability challenge: developing technologically superior aircraft at affordable cost.

Simulation Based Design (SBD) offers a promising strategy for tackling the affordability challenge by rectifying the deficiencies of the traditional design practices. The deficiencies can be traced to a heavy reliance on experimental tests to generate data for configuration design and on developing physical prototypes to verify functional and operational characteristics which render the entire development effort too long and too expensive to meet customer expectations. A SBD effort employs integrated multi-disciplinary models, computational simulations, and simulators to guide the development of a virtual prototype (VP) with a degree of functional realism comparable to a physical prototype. The key measure of success is the level of fidelity with which a VP reproduces the characteristics of the real airplane. Clearly, realistic predictions of the requisite characteristics hold the key to success. And generating realistic predictions requires increasingly sophisticated high-fidelity physics-based modeling & simulation methods that exploit the ever increasing power of high-performance computers.

CFD plays a pivotal role in realizing the full potential benefits of SBD. CFD provides aerodynamic forces, moments and stability & control parameters required to assess VP performance to ensure that the final design will be capable of successfully carrying out the intended mission. Also, CFD provides inputs to several other engineering disciplines supporting the design effort. For example, airframe structural design requires steady and unsteady loads that CFD can provide. Flight control system design requires airplane response to control commands, and CFD can provide incremental forces and moments due to control surface deployment. In addition, CFD can provide on- and off-body data for an improved understanding of the flow features which offers valuable guidance for design modifications. It is worth noting that there is one design activity, namely, shape optimization, for which CFD is uniquely suited whereas any experimental testing based approach is totally inadequate. Of course, the key to success is: credible data.