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CFD-Based Flow Analysis around the Multi-Body Segments Optimized Using Rigid Body Fitting Method for Robotic Fish Design
Published in Rik Das, Mahua Banerjee, Sourav De, Emerging Trends in Disruptive Technology Management for Sustainable Development, 2019
P. Raviraj, S. Raja Mohamed, Adetan Oluwumi
Undulatory mode is the one that is widely adapted by many fish as it generates a wave to propel using their body and fins faster than their swimming speed. Interestingly, if the speed of the travelling wave is higher, it moves in the forward direction, and if it decreases, then it moves in the backward direction. Vortex shed by the wave-like movement is measured by the Strouhal number, which, again, ia a dimensionless parameter representing the ratio of unsteady to inertial forces. Finally, to calculate the efficiency of swimming, propulsive forces are to be compared with respect to unique swimming characteristics of fish, using Froude efficiency. It is being calculated against the amount of work done to push forward and the total work done for locomotion along with other induced forces.
Force-System Resultants and Equilibrium
Published in Richard C. Dorf, The Engineering Handbook, 2018
As a boundary layer develops, it starts in a smooth, or laminar, state. Downstream, it transforms into a turbulent state, where the flow is irregular and contains eddies. Various physical conditions, such as wall or surface roughness or upstream turbulence, will affect the speed of this transition. In smooth-walled pipes, laminar flow occurs for Reynolds numbers (Re) of less than 2000, with fully developed turbulence for Re greater than 4000. The Reynolds number is a dimensionless number developed from dynamic similarity principles that represents the ratio of the magnitudes of the inertia forces to the friction forces in the fluid. Re= inertia force friction force
Fatigue life assessment of reinforced concrete members considering bond-slip
Published in Günther Meschke, Bernhard Pichler, Jan G. Rots, Computational Modelling of Concrete Structures, 2018
The theory of dimensional analysis and intermediate asymptotic can be used for the development of mathematical formulation in a given physical problem. Firstly, Dimensional analysis considers various variables that governs the physical phenomenon under consideration and converts them into dimensionless numbers having total physical dimension equal to unity. Use of dimensionless numbers is advantageous as it reduces the number of variables which are needed to define a physical problem and provides physical meaning of the parameters which leads to a better understanding of the phenomenon if formed correctly. Moreover, the use of dimensionless number can reduce the quantity of experimental data required. Secondly, the application of theory of self-similarity to this dimensionless numbers can eliminate either too small or large terms. However, depending on the physical problem considered, different self-similar solutions can be derived.
Heat and mass transfer in thin nanoliquid film over an unsteady stretching sheet in a porous medium with chemical reaction and thermal radiation
Published in International Journal of Ambient Energy, 2022
Dulal Pal, Debranjan Chatterjee, Surya Kanta Mondal
The similarity transformation has been employed to convert the nonlinear partial differential equations to nonlinear ordinary differential equations by defining some non-dimensional quantities. These non-dimensional quantities (without any physical units), i.e. which are a set of dimensionless numbers those play an important role in analysing the flow behaviour of the nanofluid. Such a dimensionless number is typically defined as a product or ratio of quantities which do have units, but all the units cancel out. The values of these dimensionless numbers are chosen in order to compare the present results with the published paper and looking into the physical quantities validity of the chosen values. Numerical results for velocity profile, temperature gradient and concentration gradient are drawn to analyse the effects of different physical parameters for the flow of thin nanofluid film over an unsteady stretching sheet embedded in a porous medium in the presence of chemical reaction and thermal radiation. Table 1 revealed the temperature distribution, concentration distribution and film thickness for different values of unsteadiness parameter, Brownian motion parameter and Lewis number. It is seen that for different values of the unsteadiness parameter and Lewis number, the temperature and concentration distributions converge to a fixed value of the thickness of thin film.
Effect of diffusion limitation and substrate inhibition on steady states of a biofilm reactor treating a single pollutant
Published in Journal of the Air & Waste Management Association, 2019
In this model, there are nine relevant variables: raverage (the overall degradation rate in the biofilm, gsubstrate m−2 s−1), rexternal (the degradation rate assuming external conditions throughout the biofilm, gsubstrate m−2 s−1), ρbio, Vmax, DA, Ks, KI, cAgas H−1, and L. These include four dimensions (gsubstrate, gbiomass, m, s) and based on eq (9), leading to five dimensionless numbers (π1, π2, π3, π4, π5). Dimensionless numbers were chosen by defining ratios that have physical meaning. The following numbers were chosen:
Accuracy and comparison of standard k-ϵ with two variants of k-ω turbulence models in fluvial applications
Published in Engineering Applications of Computational Fluid Mechanics, 2018
Alireza Farhadi, Arno Mayrhofer, Michael Tritthart, Martin Glas, Helmut Habersack
Based on the racetrack flume experiment, three turbulence models were compared using the RSim-3D solver: the standard model, the classical and the improved , as described in Section 2 for three different Froude numbers. The results are provided for four cross-sections and three measurement columns (the same positions as for the GIT profiles: see Figure 1c). The Froude number is a dimensionless variable applied in fluid dynamics studies where the weight of fluid is a predominant force. Generally, this is the case for fluids with a free surface (i.e. rivers, irrigation and drainage open channels). The Froude number is a key hydraulic property in fluvial studies and has a major role in classifying the nature of the flow (i.e. state of the flow condition); therefore, three independent simulations were conducted to cover a broader scope of characteristics based on Froude number alterations.