Is Thrust Well Defined?

AMS Seminar Series

Speaker: Mark Drela, Department of Aeronautics and Astronautics, Massachusetts Institute of Technology
February 29, 2024

Presentation

Seminar Slide Deck (PDF-9.3MB)

Abstract

Conventional aircraft design and performance-estimation techniques separately compute thrust and drag, and then subtract them to obtain the net streamwise force on the aircraft for trajectory calculation. Thrust and drag are also the basis of airframer/engine-vendor business transactions. But all this runs into problems when thrust and drag are ambiguous, which is the case when the airframe and propulsor flowfields closely interact.

In the presentation, the validity and rigor of thrust-drag decomposition will be examined, and several existing thrust and drag calculation methods will also be examined and evaluated. Distinctions will be made between rigorous thrust and drag definitions, evaluation approximations, and correlation-based estimates. The feasibility of thrust and drag extraction from CFD and experimental data for powered configurations is also examined. The attributes of exactness, consistency, and uniqueness are also presented as a means of evaluating and categorizing possible alternative aircraft force decomposition approaches.

Biography

Mark Drela currently is the Terry J. Kohler Professor at the MIT Department of Aeronautics and Astronautics. He joined the faculty there in January 1986. His primary research interests are in low speed and transonic aerodynamics, design and performance of aircraft and aeromechanical devices, and computational aerodynamic design methods. He has developed a number of aerodynamic and aeromechanical design/analysis codes currently being used in the aircraft and gas turbine industries, and in academia. He teaches aircraft design fundamentals, external aerodynamics, and fluid mechanics of boundary layers at the undergraduate and graduate levels.

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