Flow-Induced Fabric Dynamics and Thermal Behavior of a Fabric-Covered Vehicle

Principal Investigator

• Roy Koomullil, University of Alabama at Birmingham (UAB)

Faculty

• Vladimir Vantsevich, UAB

Students

• TBD, UAB

Government

• Nathan Tison, US Army GVSC

Industry

• Peter Rynes, ThermoAnalytics

Project began Q4 2022.

Many of the ground vehicles of interest to the Army are fabric-covered vehicles, and many new applications of fabric covers for military vehicles are under development[1]-[6]. During the motion of these vehicles, the airflow, including strong wind and rain over these fabric materials induce aerodynamic forces which deforms the fabric. These deformations in turn change the aerodynamic forces. Therefore, the performance of these types of vehicles needs to be analyzed using coupled computational fluid and structural dynamics principles. The airflow over the vehicles that creates fluttering of the fabric material results in an increased noise signature of the vehicles. In addition, the unsteady motion of the fabric material will enhance the heat transfer to and from the cabin to the environment, which will affect the comfort level of occupants in the cabin especially in cold and hot climate zones with strong winds and precipitation. Special effects on the fabric behavior can be induced by structures such as bridge posts. The stochastic terrain, tire and suspension properties affect the vehicle structural torsional and bending oscillations and as a result, influence the forces acting on the fabric, which in turn can affect the fabric motion and heat transfer.

There are many computational modeling challenges that include: 1) The fabric is made of very thin flexible material, which causes large deformation under the action of aerodynamics forces and these large deformations are difficult to model. These deformations also impact the action of the aerodynamic forces on the vehicles. 2) An accurate prediction of the deformation requires accurate material models for the fabric material. However, selection of appropriate material models is challenging. 3) Computational modeling of the flow fields needs a body conforming mesh. Efficient mesh deformation algorithms are required to handle large deformations of fabric materials for an accurate simulation and for the stability of the solver. 4) The heat transfer rate through fabric materials is a function of the thickness and porosity of the fabric, and the fabric materials allow higher heat transfer rates compared to solid surfaces. Also, the heat transfer rate will be enhanced by fluttering of the fabric material. 5) Environmental conditions such as rain can change the forces exerted on the fabric surface, which can influence the flutter behavior and heat transfer. This necessitates a two-phase flow simulation. 6) The terrain and speed of the vehicles influence the forces acting on the fabric through the structural behavior of the vehicle. All these aspects need to be considered and analyzed in a coupled approach to understand the complex flow around ground vehicles with fabric covers. These aspects clearly show that this is a multi-disciplinary problem, and accurate modeling of different disciplines and accurate transfer of information across disciplines is required to tackle this class of problem.

The goal of the proposed study is to analyze the complex flow features around vehicles with fabric covers and to produce a methodology for modeling and simulation of the effect of heat transfer enhancement due to the fluttering of fabric material integrated with vehicle multi-degree structural dynamics on stochastic terrain using a numerical approach. This requires the development and validation of a methodology to analyze the complex flow field using an FSI approach.

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