A theoretical analysis about the effect of aspect ratio on single-phase laminar flow in rectangular ducts

Xing, Dianchuan; Yan, Changqi; Wang, Chang; Sun, Licheng

doi:10.1016/j.pnucene.2013.01.003

Cited by 20 publications

(6 citation statements)

References 21 publications

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“…Dou 9 proposed an energy gradient method to clarify the mechanism of flow from laminar flow to turbulent flow and to analyze flow instability. In accordance with the energy gradient method, 9–14 energy gradient function is a dimensionless field, which is expressed as follows.…”

Section: Universal Energy Gradient Methodsmentioning

confidence: 99%

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Large eddy simulation of energy gradient field in a centrifugal pump impeller

Chen

Zhu

Dou

et al. 2018

Proceedings of the Institution of Mechanical Engineers, Part C:

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Large eddy simulation of the fluid flow in a centrifugal pump impeller is conducted at design load and quarter load, and the energy gradient field is analyzed to reveal the behavior of internal flow. A universal equation for calculating the energy gradient function, which is defined as the ratio of energy increase (transversal gradient of the mechanical energy gradient) to energy loss (stream-wise gradient of the work done by shear stress), is adopted. Research results show that positive and negative 0.3 for the logarithm of energy gradient function are critical values that reflect dominant energy increase and dominant energy loss, respectively. The large eddy simulation results indicate that the magnitude and shape of energy gradient field are affected by turbulent fluctuation. The energy gradient field in the impeller at mid-height has more small-scale features than those in the impeller at zero and one heights. The regions of dominant energy increase and dominant energy loss are highly distinct at both design load and quarter load. In some large areas, neither dominant energy increase nor dominant energy loss is observed at quarter load in the impeller passage. These results, which are mainly attributed to a highly separated flow, are not evident at design load. The region of dominant energy increase at design load is larger than that at quarter load, particularly close to the volute. The magnitude of mean logarithm of energy gradient function at quarter load is evidently smaller than that at design load, but its value remains higher than 1.0.

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Section: Universal Energy Gradient Methodsmentioning

confidence: 99%

“…11 Subsequently, the energy gradient method has been utilized in several other flows. 12–14 However, the studies have shown that the energy gradient function formula differs for driven by pressure or shear flows. However, both pressure and shear flows appear in the flow field of centrifugal pump impeller.…”

Section: Introductionmentioning

confidence: 99%

Large eddy simulation of energy gradient field in a centrifugal pump impeller

Chen

Zhu

Dou

et al. 2018

Proceedings of the Institution of Mechanical Engineers, Part C:

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“…The width of the channel has a lower limit. Edge effects of the side walls are negligible when the width is at least 10 times the gap height [36,37]. The width of the channel has limited effect on the range but determine the flow rate.…”

Section: Design Of Measuring Geometrymentioning

confidence: 99%

Capillary rheometer for magnetic fluids

Allebrandi¹,

Lampaert

Ostayen

2019

J. Micromech. Microeng.

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Magnetic fluids have been around since the 1940s. They come in different forms: magnetorheological fluids (MR fluids) and ferrofluids. MR fluids characterise themselves by having a large change in viscosity under the influence of a magnetic field. Ferrofluids have a significantly smaller change in viscosity, however ferrofluids are colloidal suspensions. After their discovery many applications followed, such as the MR clutch, magnetic damper and bearing applications, in which the fluids are subjected to ultra high shear rates. Little information is available on what happens to the rheological properties under these conditions. In general, the characteristics determined at lower shear rates are extrapolated and used to design new devices. Magnetic fluids have potential in the high tech and high precision applications and their properties need to be known in particular at shear rates around 106 s−1. Commercially available magnetorheometers are not able to measure these fluids at ultra high shear rates and are limited to 105 s−1. Therefore a new magnetorheometer is required to measure ultra high shear rates. In this paper the physical limitations of current measuring principles are analysed and a concept is designed for ultra high shear rate rheometry in combination with a magnetic field. A prototype is fabricated and the techniques used are described. The prototype is tested and compared to a state of the art commercial rheometer. The test results of the prototype rheometer for magnetic fluids show its capability to measure fluids to a range of 104 s−1– s−1 and the capability to measure the magnetorheological effect of magnetic fluids.

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“…Several methods can be adopted to study energy losses [19][20][21][22], and among them, entropy production theory is a crucial method to study fluid machinery [23][24][25]. Dou [26] introduced an energy gradient method to express the ratio between energy increase and energy loss, and it has been utilized in several flows [27][28][29][30][31][32]. Recently, Chen et al [33] investigated the energy change field in the centrifugal pump impeller and proposed the concepts of dominant energy increase (DEI) and dominant energy loss (DEL), whose phenomenon is obviously different between a quarter and design loads.…”

Section: Introductionmentioning

confidence: 99%

Evolution Characteristics of Energy Change Field in a Centrifugal Pump during Rapid Starting Period

Chen

Zhang

2022

Energies

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Although the energy change field in the centrifugal pump has been investigated under quasi-steady conditions (QSC), equivalent information is not yet known during the rapid starting period (RSP). A centrifugal pump loop system is constructed to investigate the energy change field in the centrifugal pump during RSP. The RSP is selected as a linear rotational speed from 0 rev/min to 2900 rev/min (design rotational speed) and a constant valve opening of 0.569. Results show that the flow rate lags behind the pump head value with the linear increase in rotational speed. The large values of partial derivations of mechanical energy in normal and tangential components are mainly concentrated at the impeller outlet, whose position is insensitive to rotational speed. The region of dominant energy loss is negatively correlated with rotational speed, and an opposite phenomenon is observed in the region of dominant energy increase. With the rotational speed increasing, the mean energy gradient function in the pump impeller and pump volute gradually increases, and the slope of the former is less than that of the latter. After reaching the design rotational speed, the energy change field gradually approaches that under quasi-steady conditions.

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A theoretical analysis about the effect of aspect ratio on single-phase laminar flow in rectangular ducts

Cited by 20 publications

References 21 publications

Large eddy simulation of energy gradient field in a centrifugal pump impeller

Large eddy simulation of energy gradient field in a centrifugal pump impeller

Capillary rheometer for magnetic fluids

Evolution Characteristics of Energy Change Field in a Centrifugal Pump during Rapid Starting Period

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