Computational Aero-sciences Laboratory

Research Areas

Jets are free shear layers harboring a rich set of physical phenomena including vorticity dynamics, turbulent mixing and acoustic emissions.
We utilize experimentally anchored high-fidelity simulations to understand the evolution of coherent structures and fine-scale turbulence in low-subsonic to high supersonic operating conditions.
These studies are of relevance to thrust and noise control in commercial turbofan as well as military-style turbojet engines.

Exhaust jets produce a lot of sound
A first principle-based noise source identification and control is still an active field of research
We use a novel fluid-thermodynamic (FT) decomposition to delineate the feeble but highly detrimental acoustic component from the more energetic hydrodynamic component
This makes quantification of sound and identification of its sources significantly easier, and even yields insight into its controllability

Delineated turbulence and sounds fields of a jet -

Linear dynamics of Navier-Stokes equations yield significant insights into the stability of fluid systems, without doing expensive simulations
Shown is a classical lid-driven cavity problem with its leading instability mode
We explore operator and operator-free methods to expand the utility of linear analysis to compressible flows in three-dimensional space
This is critical in identifying unsteadiness and coherent structures in relatively complex flows of practical interest

Mean flow perturbation (MFP) is an operator-free perturbation technique which gives accurate estimates of leading scales of unsteadiiness in 3D flows
It has also been shown to accurate capture prominent acoustic emissions from free-shear layers

Global stability analysis -

Numerical linearization instability mode extraction

High speed flows, generally above Mach 4 are qualitative different from subsonic and supersonic flows in terms of stability and physical characteristics
Futuristic civilian transport, space exploration and military technology all relies on accurate prediction and control of fluid flow in this regime
A major problem encountered here is transition - transition induces increased heating and drag on high-speed vehicles
We study the role of instabilities in perturbing these flows, causing transition to turbulence

A flared cone model - nonzero pressure gradient boundary layer Mach 6 NASA Compression corner - Shock=boundary-layer integration Mach 5.4

Theoretical and numerical analysis of radiation form cooled-hypersonic boundary layers

Turbulent spots and their evolution

3-D, Unsteady, Compressible Navier-Stokes equations solved on curvilinear coordinates

Temporal Schemes:

Explicit - Rk3

Implicit - B&W

Spatial schemes:

Smooth solution fields:
- 6th order compact scheme
- 8th order Pade filter
- 5th/7th order WENO reconstruction
Compressible scenarios – shock dynamics
- Roe flux calculation
- 3rd order spatial reconstruction – MUSCL based
- van- Leer harmonic limiter for stabilization
High-fidelity computations for transition and turbulent flows
- Hybridization of compact schemes with the Riemann solver – informed by shock detection routines

Characterize and quantify the performance of aero-propulsion systems
Utilize theorical models and simplified analyses to identify sensitive flow features
Employ turbulence modeling and high-fidelity simulations to evaluate performance deviations in relevant systems
Current flow problems studied include:
Non-axisymmetric, heated, over-expanded jets
Supersonic inlets