Poiseuille flow across an eccentrically confined stationary/rotating cylinder

Prasad, K. Maruthi; Agrawal, Amit; Sharma, Atul

doi:10.1016/j.oceaneng.2013.07.025

Cited by 4 publications

(1 citation statement)

References 22 publications

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“…For instance, Bourguet & Jacono (2013) revealed that the symmetry breaking induced by a rotating unconfined cylinder may impact the hydrodynamic instabilities, for example by suppressing the von Kármán street at high rotational speed. Similar effects on the flow topology were observed with a rotating confined cylinder (Camarri & Giannetti 2010), where the eccentricity of the rotating axis may enhance asymmetries (Prasad, Agrawal & Sharma 2013). Such studies have spread to many fluid problems involving the growth of flow oscillations, such as surface waves generation (Feng & Sethna 1989;Simonelli & Gollub 1989), oscillations of rotating droplets (Busse 1984;Cummings & Blackburn 1991) or hydrodynamic instabilities in elliptic pipes (Davey & Salwen 1994).…”

Section: Introductionmentioning

confidence: 63%

Symmetry breaking of azimuthal thermoacoustic modes: the UQ perspective

et al. 2016

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Since its introduction in the late 19th century, symmetry breaking has been found to play a crucial role in physics. In particular, it appears as one key phenomenon controlling hydrodynamic and acoustic instabilities in problems with rotational symmetries. A previous paper investigated its desired potential application to the control of circumferential thermoacoustic modes in one annular cavity coupled with multiple flames (Bauerheim et al., J. Fluid Mech., vol. 760, 2014, pp. 431–465). The present paper focuses on a similar problem when symmetry breaking appears unintentionally, for example when uncertainties due to tolerances are taken into account. It yields a large uncertainty quantification (UQ) problem containing numerous uncertain parameters. To tackle this well-known ‘curse of dimensionality’, a novel UQ methodology is used. It relies on the active subspace approach to construct a reduced set of input variables. This strategy is applied on two annular cavities coupled by 19 flames to determine its modal risk factor, i.e. the probability of an azimuthal acoustic mode being unstable. Since each flame is modelled by two uncertain parameters, it leads to a large UQ problem involving 38 parameters. An acoustic network model is then derived, which yields a nonlinear dispersion relation for azimuthal modes. This nonlinear problem, subject to bifurcations, is solved quasi-analytically. Results show that the dimension of the probabilistic problem can be drastically reduced, from 38 uncertain parameters to only 3. Moreover, it is found that the three active variables are related to physical quantities, which unveils underlying phenomena controlling the stability of the two coupled cavities. The first active variable is associated with a coupling strength controlling the bifurcation of the system, while the two others correspond to a symmetry-breaking effect induced by the uncertainties. Thus, an additional destabilization effect appear caused by the non-uniform pattern of the uncertainty distribution, which breaks the initial rotating symmetry of the annular cavities. Finally, the active subspace is exploited by fitting the response surface with polynomials (linear, quadratic and cubic). By comparing accuracy and cost, results prove that 5 % error can be achieved with only 30 simulations on the reduced space, whereas 2000 are required on the complete initial space. It exemplifies that this novel UQ technique can accurately predict the risk factor of an annular configuration at low cost as well as unveil key parameters controlling the stability.

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Section: Introductionmentioning

confidence: 63%

Symmetry breaking of azimuthal thermoacoustic modes: the UQ perspective

et al. 2016

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Flow past a near-wall retrograde rotating cylinder at varying rotation and gap ratios

Wang

Yuan

et al. 2018

Ocean Engineering

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Modeling the shear rate and pressure drop in a hydrodynamic cavitation reactor with experimental validation based on KI decomposition studies

Badve

Alpár

Pandit

et al. 2015

Ultrasonics Sonochemistry

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A mathematical model describing the shear rate and pressure variation in a complex flow field created in a hydrodynamic cavitation reactor (stator and rotor assembly) has been depicted in the present study. The design of the reactor is such that the rotor is provided with surface indentations and cavitational events are expected to occur on the surface of the rotor as well as within the indentations. The flow characteristics of the fluid have been investigated on the basis of high accuracy compact difference schemes and Navier-Stokes method. The evolution of streamlining structures during rotation, pressure field and shear rate of a Newtonian fluid flow have been numerically established. The simulation results suggest that the characteristics of shear rate and pressure area are quite different based on the magnitude of the rotation velocity of the rotor. It was observed that area of the high shear zone at the indentation leading edge shrinks with an increase in the rotational speed of the rotor, although the magnitude of the shear rate increases linearly. It is therefore concluded that higher rotational speeds of the rotor, tends to stabilize the flow, which in turn results into less cavitational activity compared to that observed around 2200-2500RPM. Experiments were carried out with initial concentration of KI as 2000ppm. Maximum of 50ppm of iodine liberation was observed at 2200RPM. Experimental as well as simulation results indicate that the maximum cavitational activity can be seen when rotation speed is around 2200-2500RPM.

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Poiseuille flow across an eccentrically confined stationary/rotating cylinder

Cited by 4 publications

References 22 publications

Symmetry breaking of azimuthal thermoacoustic modes: the UQ perspective

Symmetry breaking of azimuthal thermoacoustic modes: the UQ perspective

Flow past a near-wall retrograde rotating cylinder at varying rotation and gap ratios

Modeling the shear rate and pressure drop in a hydrodynamic cavitation reactor with experimental validation based on KI decomposition studies

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