AE Seminar

Measurement of Dynamic Inflow States of a Rotor in Hover

featuring

Jayant Sihori

Professor, Department of Aerospace Engineering and Engineering
Mechanics| University of Texas at Austin

Thursday, March 12

11:00 a.m. - 12:00 p.m.

Guggenheim 442

About the Seminar:

The loads and wake of a rotor undergo a transient response in response to changes in pitch inputs.
This response can be represented by a dynamic inflow model that relates perturbations in rotor
forces and moments to perturbations in inflow states. Several dynamic inflow models have been
proposed in the literature. While these models have usually been validated by indirect
measurements such as rotor flap response, direct measurements of the transient rotor wake are
lacking.
This presentation describes measurement of the transient wake of a rotor with particle image
velocimetry, using a novel phase-resolved, under-sampling approach. Dynamic collective pitch
inputs were introduced to a 2m diameter rotor as stepped sines with an amplitude of 1°, at
frequencies of 0.0/rev, 0.2/rev, 0.3/rev, 0.4/rev, 0.6/rev, and 0.7/rev. The flow fields were
measured at specific azimuths at each excitation frequency. Rotor thrust was measured at each
operating condition. The deformed shape of the rotor blades was measured using digital image
correlation and the eigenmodes were extracted using operational modal analysis. From the
measured flow fields and rotor loads, the mean inflow states were extracted and used to calculate
the corresponding Pitt-Peters dynamic inflow coefficients.

About the Speaker:

Jayant Sirohi is a Professor in the Department of Aerospace Engineering and Engineering
Mechanics at the University of Texas at Austin. He got his PhD in Aerospace Engineering in
2002 and was an Assistant Research Scientist at the University of Maryland, College Park from
2002-2007. During this time, he worked on numerous projects related to Smart Structures and
Rotary-wing Micro-Aerial Vehicles. Subsequently, Dr. Sirohi worked at Sikorsky Aircraft
Corporation, where he was a Staff Engineer in the Advanced Concepts group. At UT Austin, Dr.
Sirohi works on rotary-wing experimental aeromechanics, smart structures, plasma flow control
and aeroelasticity. He is a member of ASME and SEM, an Associate Fellow of AIAA, and a
Technical Fellow of the Vertical Flight Society.