FDS: PROTEG - Adjoint based Optimisation of Thermal Comfort

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PROTEG - Adjoint based Optimisation of Thermal Comfort

Background

The primary aim of the project ''Adjoint based sensitivity analysis and thermofluiddynamic optimisation of climate comfort and air-ducting equipment'' is the development of a simulation tool to support the control and optimisation of climate comfort and ventilation systems using viscous CFD in combination with gradient-based adjoint sensitivity-analysis strategies.

Special emphasis is given to the introduction of comfort criteria next to energy effienciency aspects for the definition of the objective function. Since traditional RANS-based simulation strategies are known to be a major contributor to predictive deficiencies experienced already during the primary flow, the approach will also focus upon an efficient transient simulation strategy.

Methodology

The methodology is based upon the continuous-adjoint formulation using both, shape and topology optimisation. A typical geometry under investigation refers to the air-distribution box illustrated in Fig. 1. The flow enters the box through centred duct, passes through a baffle/restrictor segments and enters the passenger cabin via a sequence of air-outlet sections. Both, the baffle segments and the shape of the airbox are subjected to an optimisation.

Fig. 1: Stream traces inside an exemplary geometry (air-distribution box).

Exemplary Results

The below given figures outline the results obtained by a topology optimisation of an air-distribution box at Re=28 000 (turbulent steady-state flow). Accordingly, the baffle/restrictor segments associated to each outlet section (cf. Fig. 1) have been modelled using a prorous media. The prorosity is optimised using adjoint topology optimisation strategies and the related changes are subsequently translated into changes of the real baffle parameters.

The figures compare the inital with the final design. The upper part of figure 2 shows the flow through the initial design. The lower part of figure 2 displays the result for an optimised variant which features an improved level of homogeneity along the 17 outlet sections. Details included refer to the streamlines (coloured with the velocity magnitude), the porosity (normalised by the initial value) and the flow homogeneity along the outlets by means of the deviation from the average velocity. Figure 3 provides a close-up of the differences with respect to the predicted homogeneity - which should ideally vanish - along the outlets. Notice, that the optimisation has been performed utilizing an efficient piggy-bag solution approach for the adjoint problem.

Fig. 2: Results of a topology optimisation of an air-inlet box (top: initial configuration, bottom: optimised configuration, objective function = flow homogeneity at outlet).

Fig. 3: Close-up of predictive achievements with respect to the deviation from the average velocity at the outlet (top: initial configuration, bottom: optimised configuration, objective function = flow homogeneity at outlet).

Funding

The PROTEG project is funded by the German Ministry of Economy and Technology (BMWi) under the aegis of LUFO4 framework program. The work is performed in collaboration with AIRBUS and the DLR institute for Aerodynamics and Flow Technology.