Special Issue on Industrial Applications of Computational Fluid Dynamics

The CFD (Computational Fluid Dynamics) method can be used in various areas that concern almost every field of technology, including water bodies, air spaces, as well as technical devices and machines. Fluid drives, both pneumatic and hydraulic, are commonly used to drive stationary and mobile machines. The advantage of hydraulic drives is the ability to obtain high forces and torques with relatively small dimensions. These systems can also efficiently cooperate with computer control systems, which is essential, for example, in implementing precise operational movements of machines and automation of machining or production processes. The development of both hydraulic and pneumatic drives strives to achieve higher and higher efficiency, which involves reducing energy demand, maximizing the operational range and ensuring more accurate and faster working movements. Challenges related to the development of hydraulic drives also include ensuring proper oil filtration and tightness of the system, as well as eliminating leaks into the atmosphere. Modern systems remain completely tight even at high pressures and high workloads, which is crucial in minimizing the negative impact on the environment. In contrast, in the case of pneumatic systems, the compressed air can be released directly into the atmosphere, so the problem of harmful external leaks does not occur. The CFD method has a particularly significant impact on the development of modern research in the field of hydraulics and pneumatics. It allows numerical determination of the fluid streamlines, the pressure and velocity distribution, as well as the flow forces. With this knowledge, one can modify the parameters of the working fluid stream and thus influence the flow characteristics of devices such as valves or actuators.

Special Issue “Industrial Applications of Computational Fluid Dynamics” edition I contains seven articles that cover a wide range of CFD applications. One of the important tasks carried out using CFD is reducing energy consumption. Tadas Vengalis and Vadim Mokšin in [1] reduced the energy consumption of the refrigeration device by approximately 30%. In turn, Zhu et al. [2] presented an air-assisted transport mechanism for canvas-type material. The authors demonstrated that a working medium in the form of air can be used in transport devices. CFD analysis allowed them to build a device that lifts and moves smoothly. This work also constitutes a reference point for the development of the feeding mechanism designed for automatic sewing and cutting machines. Regarding research on new technological solutions for the usage in tanks and water bodies, a promising design is the Egget^® closed floating cage [3]. It is an innovative structure that is egg-shaped and floats vertically. One of the most significant research challenges was determining the hydrodynamic load. Hence, a scaled model was built, and the CFD with the Volume of Fluid (VOF) technique was used. The simulation was focused on estimating the resistance coefficient for steady flow with various velocities and Reynolds numbers. This allowed the required data to be obtained. The results of simulations and experimental tests were then compared, achieving a high level of agreement. The flow-related phenomenon known as cavitation is usually difficult to study experimentally. Its prevention using CFD analysis is presented in the work [4]. The object in this study is the oil film between friction discs treated with an arranged hexagonal cavity texture. The research aims to analyse the oil flow behaviour in the rotary disc system. A finite difference algorithm determines the velocity and pressure of the oil film, while the pressure coefficient of the flow field is calculated to predict the cavitation initial position at different texture distribution densities. To simulate the cavitation process and verify the numerical analysis, a 3D model was created and calculated in CFX software (ANSYS, Canonsburg, PA, USA). Moreover, an innovative application of the CFD method was its usage in the design of LNG evaporators. The authors in [5] determined the aerodynamic drag coefficients for the different number of longitudinal fins of a tube with the various wind directions taken into consideration. Based on the CFD results, the aerodynamic drag coefficients of the analysed profiles were determined. The numerical outcomes were compared with experimental results obtained on a test bench in a wind tunnel. The determined aerodynamic resistance coefficients for various cross-sections of finned pipe profiles can be used to calculate the wind force acting on individual profiles. CFD method is of great importance in designing and testing various types of hydraulic valves. In this regard, they are mainly pressure or flow control valves. Flow control valves are designed to maintain a constant flow rate regardless of the changing pressure. The proposed three-way valve [6] allows the required flow rate to be held at a supply pressure slightly higher than the load pressure. This work included building mathematical and simulation models, conducting numerical simulations in Ansys/Fluent and Matlab/Simulink environments and experimental verification of results using a valve prototype on a test bench. The main contribution of the work was to present a proposal for a new constructional solution of a valve and estimate its operational characteristics. In turn, the article [7] presents a proposal and numerical analysis of a hydraulic system consisting of one pump with constant capacity supplying many receivers in the form of hydraulic motors, using the example of a rail grinder. The proposed approach required splitting the fluid stream, which was achieved using 2-way flow control valves. As part of the preliminary CFD tests, the pressure and speed distributions of the flow control valve were obtained, and the nozzle flow coefficients were determined as a function of the valve spool position. Then, a mathematical model of the system was formulated, which was used to build a simulation model in the Matlab/Simulink environment. During subsequent simulations, the system’s ability to achieve the assumed performance was verified, and operational parameters, as well as energy efficiency, were examined in the given load range. The results showed that the system was able to effectively perform the required work cycles with sufficient speed and accuracy.

The works using the CFD method presented in articles [1,2,3,4,5,6,7] show a wide range of its applications, using a working medium in the form both gas and liquid. The obtained results allow unfavourable phenomena such as cavitation to be eliminated and new innovative solutions for valves and other equipment to be created with improved operating parameters and lowered energy consumption. We warmly thank the authors for sending original works showing new, innovative solutions for the industry. We encourage for further cooperation. New functionalities of programs such as Ansys/Fluent or ANSYS/CFX create opportunities for further development of CFD technology and the performance of increasingly complex and more accurate analyses.