In the present paper, molecular dynamics simulations were performed to study the influence of two temperature control strategies on water flow behaviour inside planar nanochannel. In the simulations, the flow was induced by the force acting on each water molecule in the channel. Two temperature control strategies were considered: (a) frozen wall simulations, in which the dynamics of confining wall atoms was not solved and the thermostat was applied to the water, and (b) dynamic wall simulations, in which the dynamics of confining wall atoms was solved, and the thermostat was applied to walls while water was simulated in the microcanonical ensemble. The simulation results show that the considered temperature control strategies has no effect on the shape of the water flow profile, and flow behaviour in the channel is well described by the Navier–Stokes equation solution with added slip velocity. Meanwhile, the slip velocity occurring at the boundaries of the channel is linearly dependent on the magnitude of the flow inducing force in both frozen wall and dynamic wall simulations. However, the slip velocity is considerably greater in simulations when the wall dynamics are solved in contrast to the frozen wall simulations.

A numerical investigation of flow topology in open-type cavities with length-to-depth ratio L/h₁ = 4 was performed in the Reynolds number range of 10–1000. Cavities with differently rounded corners were chosen for simulation. Three-dimensional numerical simulations were performed to analyse flow topology in different planes. A series of experiments was performed to ensure the validity of numerical simulations. Both numerical simulations and physical experiments were conducted with water as the working fluid. Since the results agreed acceptably, further simulations were performed. The main goal of this study was to investigate and highlight the influence of rounded cavity corners on the topology and stability of flow. Analysis revealed that fully rounded upper cavity corners decrease pressure loss compared to other investigated cases; therefore, the velocity of the main flow is increased. Additionally, fully rounded upper corners form a notably smaller recirculation zone compared to other investigated cases. Flow stability analysis showed that fully rounded cavity bottom corners negatively impact flow stability by increasing the intensity of turbulence.

The fundamental cause of diabetic limbs’ problem is insufficient blood supply. The aim of the current work was to experimentally and numerically investigate the blood flow velocity and pressure changes in the channel during vibrational excitation. Th

A study of fluid flow in structured channels plays an important role in solving most fluid dynamics problems. The knowledge of the flow structure in separate cavities can be used to intensify mixing in microreactors and microelectrochemical systems (MEMS) as well as to increase heat transfer in heat sinks. Besides, knowledge about fluid flow in micro cavities could be useful to mitigate the symptoms of aneurysms. In this study, a 2D micro-particle image velocimetry (µPIV) system was used to investigate water flow in an open-type microcavity located in a straight, square cross-section (0.5 × 0.5 mm²) microchannel. Two identical micro cavities of the same cross-section as the main channel and the depth of 1 mm are oppositely located in the middle part of the channel. Because of symmetry, the flow structure of the primary vortex was investigated in only one cavity. Measurements were carried out in different planes over the entire height of the cavity at Reynolds number in the range from 100 to 3000. The flow in the channel was stationary and pulsating. Results indicate that flow in the cavity is three-dimensional. This is confirmed by velocity profile shape changes in its different transversal planes. In addition, it is determined that flow structure in the cavity depends on flow regime and flow pulsation characteristics. Velocity distribution shows that in the transverse direction there is the minimum velocity zone corresponding to the centre of the primary vortex generated by the channel flow, also the same zone is observed along the cavity in its axial plane. At low Re, such velocity distribution occurs in pulsating flow earlier than in the case of stationary flow. With increasing Re, velocity distribution in pulsating flow flattens out also more. It means that disturbed flow in the channel accelerates the formation of a stable flow structure in the cavity.

Flow stabilization and velocity uniformity in a Göttingen-type closed-circuit subsonic aerodynamic wind tunnel with an expanded test section are investigated in this study. Both experimental and numerical approaches were employed. The experiments were performed by using Laser Doppler Anemometry, Pitot tubes, and thermal anemometry. For numerical simulations, Reynolds-averaged Navier–Stokes simulations with a standard k-ε turbulence model were employed to evaluate flow characteristics in the velocity range of 0.05–20 m/s. The study shows that a properly contoured contraction nozzle suppresses inlet turbulence and ensures stable Reynolds-independent core flow. The contraction nozzle significantly accelerates and redistributes the flow, allowing rapid hydrodynamic stabilization and ensuring velocity measurements with high repeatability. These characteristics are inherent in a benchmark facility. Additionally, the study shows that the outlet-to-inlet diameter has the most prominent role in longitudinal velocity distribution in the test section. An optimal ratio of 1.10 was identified, stabilizing the pressure distribution and providing the most uniform longitudinal velocity profile. These findings offer geometry-dependent design guidelines for achieving high-quality measurements in Göttingen-type wind tunnels with expanded test sections and support accurate velocity measurement instrument calibration and aerodynamic testing.