Institut für Strömungsmechanik (ISTM)

Direct Numerical Simulation (DNS) of Heat-, Momentum- and Mass-transfer at Walls

The physics of turbulent flows near solid walls is decisive in a wide range of engineering applications. For instance, the formation of pollutants in combustion chambers and the deposition of flow-disturbing sediments in exhaust systems are strongly affected by flow phenomena occurring near solid walls. In turn, heat, momentum and mass transfer properties of such flows are also greatly influenced. Despite the importance, fundamental mechanisms and their interactions governing such processes are still poorly understood, leading to huge gaps in flow modeling and systems design.

In the context of the Collaborative Research Centre/Transregio 150 (CRC/TRR150), fluid-jets impinging on solid surfaces have been recognized as key examples to assess interactions of a complex turbulent flow field with an adjacent wall. Turbulent impinging jets are crucial in a broad range of practical applications where cooling, heating or drying of surfaces is required. Fuel injection systems and combustion chambers design can also benefit greatly from a fundamental investigation of impinging jets, as flow modeling for such applications is still far from being fully satisfactory.

The present research aims at investigating the near-wall characteristics of heat, momentum and mass transfer of turbulent jets impinging on smooth and rough solid walls by means of Direct Numerical Simulations (DNS). The numerical investigations will focus on two different jet configurations: two parallel jets with different temperature and concentrations of passive scalars impinging on a smooth solid wall (Fig. 1), and a single circular jet impinging on both hydraulically smooth and rough plates (Fig. 2). The novelty of our investigation is that, for the first time, different boundary conditions for temperature and passive scalars at the impingement wall will be assessed by means of DNS for both smooth and rough surface geometries.

The present research group is working in close collaboration with different sub-projects in the CRC/TRR150. Our fundamental research represents the digital twin of experimental investigations carried out by sub-project A06N. Combined experimental - numerical data will support the development of closure models carried out by group B03. At a later stage of the project, developed models will be tested in real-world scenarios by research groups C03 and C05.

Associated members: Alexander Stroh

 

Figure 1: Left, double square impinging jet configuration (sketch from group A06N of CRR/TRR150); right, preliminary computation of turbulent spanwise velocity fluctuations during the starting of the jet.

 

Figure 2: Axisymmetric impinging jet flow configuration.