Vibration and noise caused by pressure pulsations in the volumetric compressor manifolds are one of the most important problems in the volumetric compressor's operation. For pressure pulsation attenuation, different types of mufflers are applied using a design based on the Helmholtz resonator approach. This design is not effective for variable revolution speed compressors and in this case other pressure pulsations attenuation methods are required. Nowadays, due to the increasing application of variable speed compressors new design methods are developed. One of the possibilities to attenuate pressure pulsations over a wide range of frequencies is the introduction of specially shaped nozzles in the gas duct flow directly after the compressor outlet chamber. It is well known that a nozzle can attenuate pressure pulsations, however, it increases the compressor power at the same time. The main criterion for the nozzle selection is the highest possible attenuation of pressure pulsations coupled with the lowest possible effect on the compressor pumping power. In some cases 25-30% of the pressure damping is good enough to reach the standard requirements. The method applying CFD impulse flow simulations has been developed for the estimation of the nozzle influence on pressure pulsations for all frequencies. The FLUENT/ANSYS software has been used for the simulation. The CFD simulation requires a lot of effort for proper selection of the boundary conditions, solution methods, turbulence models, discretization methods, mesh design etc. The results are in some cases surprisingly different between different methods. In this paper the flow simulations for the nozzle flow with the connecting pipe using impulse function as a mass inflow excitation is shown. In this investigation project various models and methods have been compared and results in 2D and recalculated into 0D time only dependent functions are presented

Vibrations and noise caused by the pressure pulsations in the volumetric compressor manifolds have a high impact on the compression power requirement and the reliability of manifold operation. For the pressure pulsations attenuation, different types of mufflers are applied using a design based on the Helmholtz resonator model approach. This is particularly effective for the constant revolution speed compressors. For the widely introduced variable revolution speed compressors, other pressure pulsation attenuation methods are required. One of the possibilities to attenuate the pressure pulsations over a wide range of frequencies is the introduction of specially shaped nozzles in the gas duct flow. The CFD impulse flow simulations can be used as a tool for the estimation of the nozzle influence on the pressure pulsations damping. The direct 3D or 2D CFD simulation results are difficult to apply for this estimation. A new method has been worked out to obtain the damping coefficient for the diverse nozzle type, using the numerical simulation results of the impulse flow propagation. In this paper the application of the Levenberg-Marquardt method for damping parameter estimation is shown. This method allows fitting the attenuation curves described by damped equations to obtain damped oscillation functions from CFD results. In this paper the CFD based estimation method of pressure pulsation damping parameters is illustrated with an example of its application for a nozzle

The discrete element method (DEM) is a numerical technique used in many areas of modern science to describe the behavior of bulk materials. Terramechanics of planetary soil analogs for in situ resource utilization activities is a research field where the use of DEM appears to be beneficial. Indeed, the close-to-physics modeling approach of DEM allows the researcher to gain much insight into the mechanical behavior of the regolith when it interacts with external devices in conditions that are hard to test experimentally. Nevertheless, DEM models are very difficult to calibrate due to their high complexity. In this paper, we study the influence of fundamental model parameters on specific simulation outcomes. We provide qualitative and quantitative assessments of the influence of DEM model parameters on the simulated repose angle and computational time. These results help to understand the behavior of the numerical model and are useful in the model calibration process.

Purpose: In some types of industries, the best possible design, in terms of thermal and flow performance, determines the success or failure of the company. This applies, among others, to the sectional elements that form doors, windows or prefabricated building walls. The purpose of this paper is to show the possibilities and limitations of the different response surface methods for optimization in the case where natural convection phenomenon appears inside the sectional structures. Design/methodology/approach: A three-layered wall with air gap is used as a cross-section heat flow model. Response surface algorithms for optimization, which can be found in commercial software, e.g. ANSYS/WORKBENCH, can help to optimize geometrical structure of components to achieve bigger or smaller heat flux value. In this paper, the optimization methodology of the design of experiments (DOE) and different response surface (RS) methods are used. Findings: Optimal results obtained with the use of genetic aggregation, standard RS, Kriging, non-parametric regression and neural network methods are compared with direct CFD and analytical calculations. Different limitations and advantages of the RS methods make individual methods more appropriate for different issues. For a properly defined optimization problem, the heat flux value approximated for the optimal geometry agrees with the direct CFD simulations. Practical implications: The presented investigations show how to use response surface optimization methods for thermal optimization of the sectional elements and their applications to obtain reliable results. Originality/value: This paper presents the value of the use of RS methods in CFD-based geometry optimization. The study also shows that the RS optimization methods can approximate thermal properties under natural convection development conditions.