The effect of sub-grid scale models on the Large Eddy Simulation of a corrugated channel flow

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First and second law work production efficiency of a muscle cell

The absolute value of the muscle efficiency and its decrease over time has vital consequences. Among other diseases, heart failure, which is the leading cause of death in developed countries, is dramatically affected by muscle weakness. This paper provides an analogy between the Carnot engine and muscle to gain insight on the muscle work production process and estimate the maximum muscle efficiency under physiological conditions. An ‘ideal muscle’ model, which operates steadily and reversibly, is defined and for this model energy and exergy analyses are performed. Theoretical results are compared with the experimental measurements

Signal propagation in diffusive molecular communications over a spherical surface

Diffusive molecular communications (DMC) relies on the Brownian motion of dedicated molecules for transmitting information. The signal propagation characteristics in a DMC channel is determined by the geometries of the environment, receiver and the transmitter and their physical and chemical properties, which impose the boundary- and initial conditions on the partial differential equation (PDE) describing the diffusion process. In this work, we investigate the directional signal propagation characteristics for a point source over (or, as a special case, on) a spherical surface, that may be reflective, perfectly absorptive or partially absorptive. We derive the general solution of the PDE for this case, and validate it via particle based simulations. Our results can be employed to determine the signal propagation characteristics in a wide range of practically relevant scenarios, for which we investigate the effect of the system parameters on the directivity of the signal propagation

Channel characteristics for diffusive molecular communications in a spherical shell

Diffusive molecular communication (DMC) is a bio-mimicking communications paradigm that exploits the Brownian motion of dedicated information carrying molecules for signal transmission. The characteristics of the communication channel in a DMC system heavily depends on the transmitter and receiver mechanisms, on the medium of propagation and its boundaries, and on the way they interact with the molecules. In this work, we investigate the DMC channel in a spherical shell, with inner and outer surfaces which may be partially or perfectly absorptive, or reflective, where either of the boundary surfaces can be considered as the DMC receiver. These geometry and boundary conditions can be used to model a variety of practically relevant scenarios, which are investigated in detail. We derive the general parametric solution of the partial differential equation for this case and provide, for the first time in the literature, expressions for the resulting channel response. We verify the results of our analysis numerically via particle based simulations

Biothermodynamics: principles and application

Over the past several decades there has been increasing research interest in thermodynamics as applied to biological systems. This concerns topics such as muscle work and internal energy such as fat and starch. Applications of the first and second laws of thermodynamics to the human body are important to dieticians and health science experts, and applications of these concepts to the animal body are a major concern of animal scientists. This book covers these key topics, which are typically not covered in classic or traditional thermodynamics texts used in mechanical and chemical engineering

Experimental investigation on flows in a corrugated channel

Flows in a corrugated channel are investigated by a high-speed camera and a particle image velocimetry (PIV) system. The bottom wall of the rectangular channel was corrugated with periodic grooves while the top wall and two sidewalls were flat plates made of Plexiglas. Flow visualization data from the high-speed camera determine the critical Reynolds number to be around 1500 by examining the stability of the vortex in the groove as well as fluid ejection from the groove. The visualization data for turbulent flow also show how a vortex evolves within the groove and triggers another vortex formation in the subsequent groove, and how fluid ejected from the groove triggers another ejection from the subsequent groove. Thus, strong hydrodynamic interactions are observed between successive corrugations. In addition, PIV data provide the profiles of velocities and Reynolds stresses as a function of Reynolds number. Time-averaged streamlines show that a large, stable vortex exists in the groove for laminar flow. On the other hand, for turbulent flow, the vortex is unstable inside the groove, often prompting fluid ejection which interacts with the bulk flow. Especially the Reynolds stress of the square of velocity fluctuation in the direction normal to the bulk flow significantly increases as the fluid ejection from the groove intensifies with increasing Reynolds number

Understanding loss generation mechanisms in a centrifugal pump using large eddy simulation

Water pumps are amongst the most frequently used turbomachines, which consume about 9% of the global energy production. This paper provides insight on the loss generation mechanisms in inline centrifugal pumps operating under realistic conditions through a detailed analysis based on large eddy simulation (LES). The equations for the resolved, sub-grid and wall entropy generation terms are derived using the LES filtering and Smagorinsky-Lilly formalism. Specific exergy is calculated at the grid points. Entropy generation and exergy transfer within the flow domain are visualised to highlight the loss generation mechanisms within the pump. Results show that there is a strong component interaction. The double-bended inlet pipe initiates Dean-vortices at the eye of the impeller. This asymmetric inflow coupled with the disturbances at the cut-off cause a non-uniform flow through the blade passages. Other drivers of the asymmetrical loading of the blade passages are high leakage and unsteady and asymmetrical mass and exergy transfer between the dead zone. The paper also investigates the effect of the grid resolution on the first and second order statistics of the flow field and its turbulent characteristics. A thorough evaluation of the discretisation error is presented to provide a measure for the required grid density and demonstrate the extent and impact of the temporal and spatial discretisation error in centrifugal turbomachinery.</p

Lifespan entropy generated by the masseter muscles during chewing: an indicator of the life expectancy?

The life span entropy concept suggests that the organisms may have a limited capacity of life span entropy generation, when they reach to that limit they die. The masseter muscles of a subject who is consuming food along the guide lines of Institute of Medicine (USA) may generate almost 1 × 105 J/K of entropy while chewing his food during his 76 years of expected life time. The masseter muscles of an obese person, who uptakes 10% more nutrients generates the same entropy about five years earlier. The cumulative entropy generation decreases as the second law efficiency of the muscle work rises. The results of this study imply that the concept of the lifespan entropy may be correct even at the individual muscle level, and may be employed to estimate the life expectancy of a person