Instability-Based Control of a Developing Trailing Vortex
Abstract
Background: Turbulent wall bounded flows play a key role in turbine cooling, energy exchange in regional climate, wind energy, HVAC, aerodynamics, drag reduction applications in underwater bodies and particle dispersion for homeland security. Although turbulent boundary layers have been studied for over 50 years, the understanding of them remains the cause of great controversy in the turbulence community. Such understanding is critical, if we are to develop practical control schemes that can help mitigate the energy penalty of turbulent boundary layers. Recent studies have shown that there are Large Scale Motions (LSMs) and Very Large Scale Motions (VLSMs) that carry more than 50% of the Reynolds stresses and kinetic energy. The largest of these motions have scales of the order of O(1?) ? L ? O(10?) and are often also referred to as superstructures. Hutchins and his team have found that these features can exceed 15? in length. Other studies on boundary layers by Castillo and his colleagues showed the importance of the initial conditions on the flow development. The hypothesis in the proposed study is to demonstrate the possibility to achieve Global Flow Control of the downstream flow by manipulating the inlet conditions in such a way to control the “superstructures”. Our team from the USA and Australia seeks to explain the mechanisms by which such complex interactions are possible, and also to explore how these superstructures can modulate the inner region and vice versa. Intellectual Merit: The proposed research consists of high Reynolds number wind tunnel experiments and highly-accurate Direct Numerical Simulations (DNS) to study spatially-developing turbulent boundary layers under the influence of different inlet perturbations (e.g., including steady and unsteady). The combined study will provide valuable data to the turbulence community from R ? 2, 500 ? 49, 000. The low Reynolds number simulations will uncover the impact of inlet perturbations on superstructures and will provide optimum configurations to consider in the moderate and high Reynolds number studies. This groundbreaking research will establish the foundations for Active Global Flow Control in wall-bounded flows. At Texas Tech University, the DNS code, which employs an innovative Dynamic Multi-scale approach for turbulent inflow generation, will be adapted to account for different inlet perturbations in extensively long domains of the O(70?). The team has access to unique world-class facilities in USA and Australia, and their collective expertise will enable a breakthrough in our understanding of wall turbulence. Broader Impact: The proposed research will advance the understanding of turbulence, increasing the fundamental knowledge of superstructures and how they are affected by different inlet conditions. Additionally, it will provide a comprehensive database available for the scientific community. It will provide new fundamental understanding and parameterizations to assist in the evaluation/assessment for industrial applications, such as film cooling technology.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Aug 12, 2016
- Source ID
- N000141512403
Entities
People
- Louis N Cattafesta
Organizations
- Florida State University
- Office of Naval Research
- United States Navy