Numerical investigation of periodic cavitation shedding in a Venturi

Charrière, Boris; Goncalves, Éric

doi:10.1016/j.ijheatfluidflow.2017.01.011

Cited by 26 publications

(20 citation statements)

References 30 publications

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“…Turbulent, cavitating flows are known to present unique modelling challenges, and the choice of turbulence model requires careful attention. Cavitating Venturi flows in particular are observed to be inherently transient [52][53][54] , exhibiting unsteady cavitation cloud shedding downstream of the throat.…”

Section: Numerical Models and Boundary Conditionsmentioning

confidence: 99%

“…As a remedy they recommended applying an arbitrary pre-multiplier to the turbulent viscosity term,  t , in order to capture unsteady effects. Arbitrary modifiers of this type have yielded success for other researchers in this field, with a number of examples showing successful capture of cavitation cloud shedding with two equation RANS approaches [54][55][56] . Similarly, high-swirl ratio cavitating vortices present a different set of modelling challenges, and are also known to exhibit periodic unsteady behaviour 57,58 .…”

Section: Numerical Models and Boundary Conditionsmentioning

confidence: 99%

See 1 more Smart Citation

110th Anniversary: Comparison of Cavitation Devices Based on Linear and Swirling Flows: Hydrodynamic Characteristics

Simpson

Ranade

2019

Ind. Eng. Chem. Res.

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The interest in cavitating flow reactors has intensified over recent years, and a significant amount of research effort has been focussed on demonstrating the potential applications of hydrodynamic cavitation. The knowledge base on the design of devices to optimise cavitation yield, performance and industrial scalability remains lacking however. It is essential to develop a sound understanding of the key hydrodynamic characteristics of cavitation devices to address these knowledge gaps. This work presents a comprehensive experimental and numerical investigation into the hydrodynamic behaviour of cavitating devices which feature linear and swirling flows. Two of the most commonly utilized cavitation device geometries are studied, namely orifice and Venturi, with and without swirl. These devices are compared to a high swirl flow device (vortex diode). A series of experimental configurations were designed with the aid of multiphase, unsteady computational fluid dynamics simulations, so as to achieve matching power input in terms of flow rate versus pressure drop across all 5 device configurations, allowing their cavitation characteristics to be directly compared on a consistent basis. High speed flow visualisation and detailed numerical predictions are presented which clearly describe the influence that key parameters such as swirl ratio and Reynolds number have on the nature of the observed cavitating flow structures. Cavitation inception conditions are described for each device, with Venturi and vortex devices shown to generate incipient cavitation at lower pressure ratios than orifice devices. Cavitation numbers are computed, which indicate that values of unity are obtained at inception across the range of devices provided that appropriate characteristic velocities are defined. Swirl is identified as an important parameter in cavitation device design, with the swirling flow device designs shown to successfully move the cavitating region away from solid surfaces towards the device axis. Importantly, this is achieved without an energy consumption penalty; the results describe how swirl can be utilized to design devices which minimise or eliminate the risk of surface erosion.

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Section: Numerical Models and Boundary Conditionsmentioning

confidence: 99%

Section: Numerical Models and Boundary Conditionsmentioning

confidence: 99%

110th Anniversary: Comparison of Cavitation Devices Based on Linear and Swirling Flows: Hydrodynamic Characteristics

Simpson

Ranade

2019

Ind. Eng. Chem. Res.

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“…By stacking these lines of data, an x-t diagram is obtained, which will be useful to describe the dynamics of the cavitation process. The x-t diagram is useful for the determination of unsteady cavitation behavior and it is a common data processing method in the field of cavitation ( Saito and Sato, 2007;Charrière and Goncalves, 2017;Budich et al, 2018 ). An example of a typical x-t diagram is shown in Fig.…”

Section: X-t Diagramsmentioning

confidence: 99%

Dynamics of partial cavitation in an axisymmetric converging-diverging nozzle

Jahangir

Hogendoorn

Poelma

2018

International Journal of Multiphase Flow

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Partial cavitation dynamics in an axisymmetric converging-diverging nozzle are investigated experimentally. Shadowgraphy is used to visualize and analyze different cavitation regimes. These regimes are generated by changing the global static pressure and flow velocity independently. Cloud cavitation is the most interesting and complex regime, because the shedding of vapor clouds is caused by two different mechanisms: the re-entrant jet mechanism and the bubbly shock mechanism. The dynamics are investigated using a position-time diagram. Using such a diagram we show that for cavitation number σ > 0.95 the cavity shedding is caused by the re-entrant jet mechanism, and for σ < 0.75 the mechanism responsible for periodic cavity shedding is the bubbly shock mechanism. Both mechanisms are observed in the transition region, 0.75 < σ < 0.95. The shedding frequencies, expressed as Strouhal numbers, collapse on a single curve when plotted against the cavitation number, except for the transition region. The re-entrant jet mechanism is a pressure gradient driven phenomenon, which is caused by a temporary stagnation point at the cavity front. This leads to stick-slip behavior of the cavity. In the bubbly shock regime, a shock wave is induced by a collapse of the previously shedded vapor bubbles downstream of the venturi, which triggers the initiation of the detachment of the growing cavity. The propagation velocity of the shock wave is quantified both in the liquid and the mixture phase by means of the position-time diagram.

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“…Divergence angle significantly changes the flow condition in a Venturi Table 1. Previous experimental study on Venturi cavitation 15,17,18,20,21,[25][26][27][28] . where p th is the pressure of the Venturi throat part and p in is the pressure of the Venturi inlet.…”

Section: Experimental Investigation Of the Dynamic Cavitation Behaviomentioning

confidence: 99%

Experimental investigation of the dynamic cavitation behavior and wall static pressure characteristics through convergence-divergence venturis with various divergence angles

Liu

Fan

et al. 2020

Sci Rep

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As a highly efficient and energy-saving cavitation method, Venturi cavitation is widely used in many industrial fields. This study synchronously investigated the cavity behavior and its corresponding wall static pressure characteristics in Venturi channels with various divergence angles to research the role of the divergence angle in cavity shape and the wall static pressure oscillation. Five rectangular Venturi channels with different divergence angles (4°, 6°, 8°, 10°, and 12°) were tested at the cavitation number (0.3–1.0). Based on the dynamic behaviour of gas–liquid interface, three cavity shedding types were identified: front shedding (I), central shedding (II) and tail shedding (III). A modified correlation for predicting average cavity length was proposed with the consideration of the effect of the divergence angle. Combined with the wall static pressure characteristics, as the divergence angle increased, the wall static pressure fluctuation in the Venturi became more intense. According to the wall static pressure oscillation characteristics, for the larger divergence angles (θ = 6°, 8°, 10° and 12°), the wall static pressure oscillation frequency was the same as the cavity shedding frequency and increased with the increase of the divergence angle. For smaller divergence angle (θ = 4°), no definite periodicity in pressure oscillation frequency could be observed.

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Numerical investigation of periodic cavitation shedding in a Venturi

Cited by 26 publications

References 30 publications

110th Anniversary: Comparison of Cavitation Devices Based on Linear and Swirling Flows: Hydrodynamic Characteristics

110th Anniversary: Comparison of Cavitation Devices Based on Linear and Swirling Flows: Hydrodynamic Characteristics

Dynamics of partial cavitation in an axisymmetric converging-diverging nozzle

Experimental investigation of the dynamic cavitation behavior and wall static pressure characteristics through convergence-divergence venturis with various divergence angles

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