One of the most important aspects of governing physical processes through rough-walled fractures is the non-linear behavior of flow. The onset of non-linear flow in rock fractures is characterized by CRITICAL REYNOLDS NUMBER, which is the main object of this paper. In this paper, the technical aspects of non-linear flow of crude oil through open rock fractures and CRITICAL REYNOLDS NUMBER were studied. These issues were studied based on the results of three-dimensional numerical simulation of the Navier-Stokes equations for crude oil flow through rough-walled fractures. The finite volume simulation of crude oil flow through three-dimensional space of rough-walled fractures was performed for a wide range of REYNOLDS NUMBERs or flow rates. The results of crude oil flow simulations were analyzed based on the Forchheimer’s law. The coefficients of energy losses due to viscous and inertial dissipation mechanisms were derived from the Forchheimer’s law regression on the results. Then, the role of linear and nonlinear energy losses with viscous and inertial dissipation mechanisms was evaluated based on the relation between REYNOLDS and Forchheimer non-dimension NUMBERs. Finally, the CRITICAL REYNOLDS NUMBER was determined for onset of non-linear flow through rough-walled fractures. The results of this study indicate that the Forchheimer’s law appropriately describes the non-linear crude oil flow through rough-walled fractures. By increasing the REYNOLDS NUMBER (or flow rate), the ratio of viscous energy lose from total energy losses decreases non-linearly and simultaneously, the inertial dissipation becomes the dominant mechanism of energy lose. The CRITICAL REYNOLDS NUMBER for crude oil is in the range of 30 to 46 for the open fractures of this study. The maximum and minimum of CRITICAL REYNOLDS NUMBER follow the minimum and maximum of inertial dissipation coefficient and also the gradient of REYNOLDS-Forchheimer curve, respectively.

Being widely ubiquitous in fluidic mediums from aquatic environments to bodies, for the sake of their mobility, microorganisms, such as bacteria and motile cells, make use of particular swimming strategies that are counter-intuitive to that of our daily life experience, given that the physics governing micrometer is different from that of macroscale physics. Living in this particular realm of supposedly zero REYNOLDS NUMBER, these microscopic creatures are constrained such that their methods of swimming as well as their sequence of strokes need to utterly satisfy the so-called scallop theorem. Considering the importance of motility for both microrobots and living creatures, this study aims to propose a model swimmer for artificial swimmers that might also be a prospective model explaining a mode of swimming for existing self-propelled natural living matters that can move forward by changing the shape of their body. The proposed swimmer is made up of three equal spheres, arranged in a triangular configuration by placing the center of each of them at the vertices of a triangle. The active links form a T-shape frame, such that the first link serves to connect two spheres, and the second link originates from the other sphere to connect it to the middle of the first link. Considering only two degrees of freedom for each link, this swimmer can translate along a straight path, by expanding or contracting its links consecutively in proper order. Obtaining the velocity of the swimmer, we study the effects of geometrical parameters of the triangle on the mean velocity of the swimmer over each cycle of motion. Finally, it will be shown that the velocity obtained here, which linearly depends on its characteristic parameters, resembles perfectly its well-known rectilinearly configured spheres counterpart, initially proposed by Najafi and Golestanian (Phys. Rev. E 69, 062901 (2004)), and its properties have been extensively studied over past years.

In the current study, three airfoils—PSU94-097, SD6060, and S2055—were analyzed for their aerodynamic performance across REYNOLDS NUMBERs (Re) ranging from 50,000 to 500,000, typical for Small Wind Turbine (SWT) blade airfoils. Results indicated that as Re increased, the aerodynamic efficiency of all modified airfoils improved. Optimal thickness-to-camber ratios (t/c) of 1.50-2.25, 2.25-3, and 0.60-1.50 for SD6060, S2055, and PSU94-097 airfoils, respectively, contributed to enhanced efficiency. PSU94-097-modified airfoil demonstrated the highest lift-to-drag ratio (CL/CD) of 151.60 at Re of 500,000. Peak CL/CD values for SD6060-modified and S2055-modified airfoils were 109.87 and 97.13, respectively. PSU94-097-modified, SD6060-modified, and S2055-modified airfoils attained peak lift coefficients (CL) of 1.534, 1.219, and 1.174, respectively. PSU94-097-modified airfoil also showed the highest peak CL across Re ranging from 50,000 to 500,000. Percentage increase in peak CL/CD across Re range of 50,000 to 500,000 was 15.8%, 16.08%, 24.43%, 17.12%, 17.30%, 17.98%, and 20.22% for PSU94-097-modified airfoil; 27.87%, 2.03%, 13.77%, 15.83%, 15.14%, 17.95%, and 17.73% for SD6060-modified airfoil; and 16.70%, 7.11%, 5.77%, 7.25%, 11.40%, 9.99%, and 6.04% for S2055-modified airfoil. In addition to enhancing the aerodynamic efficiency of airfoils and consequently increasing electricity production in wind turbines, optimizing the t/c reduces the material needed for wind turbine construction. This not only lowers the cost but also minimizes environmental impact by using fewer resources. Thus, these modifications are environmentally beneficial, contributing to sustainable development alongside improving wind turbine efficiency.

The hydrodynamic characteristics of autonomous underwater vehicles (AUVs) play a significant role in the design and analysis of their maneuverability. This paper evaluates the effects of the REYNOLDS (Re) NUMBER on the hydrodynamic characteristics of AUV for various angles of attack (AOA). To estimate the hydrodynamic parameters, a numerical modelling based on computational fluid dynamics (CFD) is employed. REYNOLDS NUMBERs between 2 106 and 150 106 were examined at-10º to 10º AOAs. Experimental tests for the same AUV in Re = 2 106 in the water tunnel were carried out for CFD validation. A comparison of the results showed an acceptable agreement between the numerical method and the experimental results. The results show that hydrodynamic parameters can be a function of Re and converge on a constant in a limited value when the Re NUMBER increases. Results of independent parameters, can be used for full-scale without the establishment of dynamic similarity.