Abstract:The effect of surface vibrations on the propulsion augmentation and resistance in the relative movement of parallel plates has been studied. The analysis was focused on monochromatic waves and laminar flows. The effectiveness of the vibrations was gauged by determining the external force required to maintain the movement of one of the plates at a prescribed velocity. It is shown that waves propagating upstream always increase the resistance but the flow response to waves propagating downstream is more intricat… Show more
“…It is interesting to note that flow modifications have a generic form regardless of the purpose of vibrations, being pumping (Floryan et al. 2021), propulsion (Haq & Floryan 2022) or resistance reduction (Floryan & Haq 2022). Figure 4.The distributions of the u -velocity modification ( u 1 ) at for groove amplitude …”
Section: Vibration-induced Velocity Field Modificationsmentioning
confidence: 99%
“…The available literature deals mainly with biological systems where analysis of the Stokes approximation for long and slow waves is relevant (Lauga 2016); see a recent review by Ali, Ullah & Rasool (2020). The first complete analysis of fast waves was given very recently (Floryan, Faisal & Panday 2021) and extended to propulsion augmentation (Haq & Floryan 2022) and resistance reduction (Floryan & Zandi 2019; Floryan & Haq 2022). There is a lack of a systematic analysis of flows in a channel with vibrating walls and identification of different flow regimes, especially from the resistance reduction point of view.…”
The effect of surface vibrations on the pressure-gradient-driven flows in channels has been studied. The analysis considered monochromatic waves and laminar flows. The effectiveness of the vibrations was gauged by determining the pressure gradient correction required to maintain the same flow rate as without vibrations. Waves propagating upstream always increase pressure losses. Flow response to waves propagating downstream is more complex and changes as a function of the flow Reynolds number. Such waves reduce losses if the Reynolds number
$Re <\ \sim\!\!100$
, but these waves must be sufficiently fast to reduce pressure losses for larger Re values. In general, the supercritical waves, i.e. waves faster than the reference flow, reduce pressure losses with the magnitude of reduction increasing monotonically with the wave phase speed and wavenumber. The need for an external pressure gradient is eliminated if sufficiently short and fast waves are used. Generally, the subcritical waves, i.e. waves with velocities similar to the reference flow, increase pressure losses. This increase changes somewhat irregularly as a function of the wave phase speed and wavenumber forming local maxima and minima. These waves can reduce pressure losses only if the Reynolds number becomes large enough. It is shown that subcritical waves with very small amplitudes but matching the natural flow frequencies produce significant pressure losses.
“…It is interesting to note that flow modifications have a generic form regardless of the purpose of vibrations, being pumping (Floryan et al. 2021), propulsion (Haq & Floryan 2022) or resistance reduction (Floryan & Haq 2022). Figure 4.The distributions of the u -velocity modification ( u 1 ) at for groove amplitude …”
Section: Vibration-induced Velocity Field Modificationsmentioning
confidence: 99%
“…The available literature deals mainly with biological systems where analysis of the Stokes approximation for long and slow waves is relevant (Lauga 2016); see a recent review by Ali, Ullah & Rasool (2020). The first complete analysis of fast waves was given very recently (Floryan, Faisal & Panday 2021) and extended to propulsion augmentation (Haq & Floryan 2022) and resistance reduction (Floryan & Zandi 2019; Floryan & Haq 2022). There is a lack of a systematic analysis of flows in a channel with vibrating walls and identification of different flow regimes, especially from the resistance reduction point of view.…”
The effect of surface vibrations on the pressure-gradient-driven flows in channels has been studied. The analysis considered monochromatic waves and laminar flows. The effectiveness of the vibrations was gauged by determining the pressure gradient correction required to maintain the same flow rate as without vibrations. Waves propagating upstream always increase pressure losses. Flow response to waves propagating downstream is more complex and changes as a function of the flow Reynolds number. Such waves reduce losses if the Reynolds number
$Re <\ \sim\!\!100$
, but these waves must be sufficiently fast to reduce pressure losses for larger Re values. In general, the supercritical waves, i.e. waves faster than the reference flow, reduce pressure losses with the magnitude of reduction increasing monotonically with the wave phase speed and wavenumber. The need for an external pressure gradient is eliminated if sufficiently short and fast waves are used. Generally, the subcritical waves, i.e. waves with velocities similar to the reference flow, increase pressure losses. This increase changes somewhat irregularly as a function of the wave phase speed and wavenumber forming local maxima and minima. These waves can reduce pressure losses only if the Reynolds number becomes large enough. It is shown that subcritical waves with very small amplitudes but matching the natural flow frequencies produce significant pressure losses.
“…It is known that energy spent on the creation of such forcing results in the reduction of pressure losses rather than overcoming these losses as in classical propulsion, e.g. heating patterns reduce frictional losses (Hossain, Floryan & Floryan 2012; Floryan & Floryan 2015; Hossain & Floryan 2016) similarly to transpiration patterns (Jiao & Floryan 2021 a , b ) and vibration patterns (Floryan & Haq 2022; Floryan & Zandi 2019). These effects can thus be viewed as alternative propulsion methods.…”
Section: Introductionmentioning
confidence: 99%
“…Several such techniques have been investigated, e.g. surface vibrations relying on the peristaltic effect , distributed wall transpiration activating nonlinear streaming tangential to the solid boundary (Jiao & Floryan 2021a,b) and thermal drift (Abtahi & Floryan 2017) which relies on the pattern interaction effect involving topography and heating patterns Inasawa et al 2021;Floryan et al 2022). It is known that energy spent on the creation of such forcing results in the reduction of pressure losses rather than overcoming these losses as in classical propulsion, e.g.…”
It is shown that thermal waves applied on the bounding surface of a horizontal slot generate a pumping effect. Reynolds stress developed by the change in the flow field due to the thermal inertia associated with the penetration of the wave into the fluid interior drives the net fluid movement in the horizontal direction. The induced flow rate increases with the wave speed, but excessive wave speed reduces it as convection becomes limited only in the near-wall area. The excessive increase of the wavelength and its excessive decrease reduce the flow rate. An increase in the wave amplitude increases the flow rate with a saturation limiting its growth. Judicious selection of the wave speed and wavelength of a thermal wave provides a means for optimizing the wave-induced pumping. The magnitude of the pumping increases with a reduction of Prandtl number.
“…Their proper combination may activate the pattern interaction effect (Floryan & Inasawa 2021), generating thermal drift (Abtahi & Floryan 2017; Inasawa, Hara & Floryan 2021). It is further known that selective vibration patterns reduce pressure losses while others increase such losses while increasing flow mixing (Floryan & Haq 2022; Haq & Floryan 2023).…”
We present a method for accurately determining the stability characteristics of spatially modulated shear layers. The algorithm can handle arbitrary commensurate states, which are not accessible to classical direct-numerical-simulation-based approaches. It uses spectral discretization of the field equations to handle field modulations and the spectrally accurate immersed boundary conditions method to handle the geometry modulations. The algorithm can deal with pattern interaction effects driven by modulations of different physical origins. Various tests demonstrate that the algorithm delivers spectral accuracy for eigenvalues and eigenfunctions. The algorithm can be easily extended to analyse many sources and patterns of modulation with minimal commitment to the user's time.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
