Friction Modeling of Flood Flow Simulations

Bellos, Vasilis; Nalbantis, Ioannis; Tsakiris, George

doi:10.1061/(asce)hy.1943-7900.0001540

Cited by 53 publications

(27 citation statements)

References 25 publications

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“…2 d we plot our measurements of for forward and reverse flow through Tesla’s conduit. For comparison, we include on this so-called Moody diagram previous results on circular pipes 45 . The two curves shown correspond to smooth pipes and one of high roughness in which wall variations measure 10% of the mean diameter.…”

Section: Resultsmentioning

confidence: 99%

Early turbulence and pulsatile flows enhance diodicity of Tesla’s macrofluidic valve

2021

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Microfluidics has enabled a revolution in the manipulation of small volumes of fluids. Controlling flows at larger scales and faster rates, or macrofluidics, has broad applications but involves the unique complexities of inertial flow physics. We show how such effects are exploited in a device proposed by Nikola Tesla that acts as a diode or valve whose asymmetric internal geometry leads to direction-dependent fluidic resistance. Systematic tests for steady forcing conditions reveal that diodicity turns on abruptly at Reynolds number $${\rm{Re}}\approx 200$$ Re ≈ 200 and is accompanied by nonlinear pressure-flux scaling and flow instabilities, suggesting a laminar-to-turbulent transition that is triggered at unusually low $${\rm{Re}}$$ Re . To assess performance for unsteady forcing, we devise a circuit that functions as an AC-to-DC converter, rectifier, or pump in which diodes transform imposed oscillations into directed flow. Our results confirm Tesla’s conjecture that diodic performance is boosted for pulsatile flows. The connections between diodicity, early turbulence and pulsatility uncovered here can inform applications in fluidic mixing and pumping.

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Section: Resultsmentioning

confidence: 99%

Early turbulence and pulsatile flows enhance diodicity of Tesla’s macrofluidic valve

2021

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“…Thus, the unified approach presented here can be easily implemented with software codes. Moreover, as the proposed switching functions are carefully chosen so that they follow Nikuradse's inflectional law of roughness, our unified approach seems to be more realistic than the classic implicitly-given 80-year-old Colebrook-White monotonic curves model [41][42][43][44][45][46]. The switching functions presented here are expressed by simple rational functions and thus do not contain computationally expensive transcendental functions.…”

Section: Discussionmentioning

confidence: 99%

Unified Friction Formulation from Laminar to Fully Rough Turbulent Flow

Brkić

Praks

2018

Applied Sciences

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This paper provides a new unified formula for Newtonian fluids valid for all pipe flow regimes from laminar to fully rough turbulent flow. This includes laminar flow; the unstable sharp jump from laminar to turbulent flow; and all types of turbulent regimes, including the smooth turbulent regime, the partial non-fully developed turbulent regime, and the fully developed rough turbulent regime. The new unified formula follows the inflectional form of curves suggested in Nikuradse’s experiment rather than the monotonic shape proposed by Colebrook and White. The composition of the proposed unified formula uses switching functions and interchangeable formulas for the laminar, smooth turbulent, and fully rough turbulent flow regimes. Thus, the formulation presented below represents a coherent hydraulic model suitable for engineering use. This new flow friction model is more flexible than existing literature models and provides smooth and computationally cheap transitions between hydraulic regimes.

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“…In the case of air flows in a pneumatic, this condition is fulfilled [19]. The formulae proposed by [26] were used to determine the Darcy friction factor λ i…”

Section: Pneumatic Transmission Line Modelmentioning

confidence: 99%

Exhaust Noise Reduction by Application of Expanded Collecting System in Pneumatic Tools and Machines

et al. 2021

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In this paper, we demonstrate how to reduce the noise level of expanded air from pneumatic tools. Instead of a muffler, we propose the expanded collecting system, where the air expands through the pneumatic tube and expansion collector. We have elaborated a mathematical model which illustrates the dynamics of the air flow, as well as the acoustic pressure at the end of the tube. The computational results were compared with experimental data to check the air dynamics and sound pressure. Moreover, the study presents the methodology of noise measurement generated in a pneumatic screwdriver in a quiet back room and on a window-fitting stand in a production hall. In addition, we have performed noise measurements for the pneumatic screwdriver and the pneumatic screwdriver on an industrial scale. These measurements prove the noise reduction of the pneumatic tools when the expanded collecting system is used. When the expanded collecting system was applied to the screwdriver, the measured Sound Pressure Level (SPL) decreased from 87 to 80 dB(A).

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Friction Modeling of Flood Flow Simulations

Cited by 53 publications

References 25 publications

Early turbulence and pulsatile flows enhance diodicity of Tesla’s macrofluidic valve

Early turbulence and pulsatile flows enhance diodicity of Tesla’s macrofluidic valve

Unified Friction Formulation from Laminar to Fully Rough Turbulent Flow

Exhaust Noise Reduction by Application of Expanded Collecting System in Pneumatic Tools and Machines

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