Reduction of pressure losses and increase of mixing in laminar flows through channels with long-wavelength vibrations

Abstract

Pressure losses and mixing in vibrating channels were analysed. The vibrations in the form of long-wavelength travelling waves were considered. Significant reduction of pressure losses can be achieved using sufficiently fast waves propagating downstream, while significant increase of such losses is generated by waves propagating upstream. The mechanisms responsible for pressure losses were identified and discussed. The interaction of the pressure field with the waves can create a force which assists the fluid movement. A similar force can be created by friction, but only under conditions leading to flow separation. An analysis of particle trajectories was carried out to determine the effect of vibrations on mixing. A significant transverse particle movement takes place, including particle trajectories with back loops. The downstream-propagating out-of-the phase waves provide a large reduction of pressure gradient and significant potential for mixing intensification. Analysis of energy requirements demonstrates that it is possible to identify waves which reduce power requirements, i.e. the cost of actuation is smaller than the energy savings associated with the reduction of pressure gradient. The fast forward moving waves provide an opportunity for the development of alternative propulsion methods which can be more efficient than methods based on the pressure difference.

On the use of transpiration patterns for reduction of pressure losses

“…Altering surface topography (Perot & Rothstein 2004) represents the former approach while the use of surface transpiration (Bewley & Alamo 2004; Min et al. 2006; Bewley 2009; Hœpffner & Fukagata 2009; Mamori, Iwamoto & Marata 2014), plasma- (Inasawa, Ninomiya & Asai 2013), sound- (Kato, Fukunishi & Kobayashi 1997) and piezo-driven actuators (Fukunishi & Ebina 2001) as well as surface vibrations (Floryan & Zandi 2019) represent the latter techniques.…”

“…Min et al. (2006), Marusic, Joseph & Nahesh (2007) and Woodcock, Sader & Marusic (2012) demonstrated that a reduction of the pressure gradient can be achieved using suction/blowing waves but that the energy cost of the creation of such waves is higher than the energy savings associated with smaller pressure gradients (Bewley 2009; Fukagata, Sugiyama & Kasagi 2009). Transpiration can also increase losses through destabilization of the laminar flow (Lee, Min & Kim 2008; Lieu, Moarref & Jovanovič 2010; Moarref & Jovanovič 2010).…”

The role of vibrations for reducing the resistance in the relative movement of parallel plates

“…An extension of this approach is based on the use of hydrophobic surfaces (Perot & Rothstein 2004). More active techniques involve the application of suitable distributed heating (Hossain, Floryan & Floryan 2012; Floryan & Floryan 2015; Floryan, Shadman & Hossain 2018), wall transpiration (Jiao & Floryan 2021), surface vibrations (Floryan & Zandi 2019), plasma actuators (Inasawa, Ninomiya & Asai 2013), sound (Kato, Fukunishi & Kobayashi 1997) or piezoelectric actuators (Fukunishi & Ebina 2001). An excellent review of some of these ideas has been given by Cattafesta & Sheplak (2011).…”

“…The creation of distributed forcing in technical systems involves the imposition of forcing patterns along fluid–solid boundaries to reduce the relative velocity of the two mediums. Known physical manifestations of these effects include nonlinear streaming created by wall transpiration (Jiao & Floryan 2021), the pattern interaction effect (Floryan & Inasawa 2021) that leads to thermal drift (Abtahi & Floryan 2017; Inasawa, Hara & Floryan 2021) and surface vibrations (Floryan & Zandi 2019). Flow relaminarization using transpiration waves (Lieu, Moarref & Jovanović 2010; Moarref & Jovanović 2010; Mamori, Iwamoto & Murata 2014; Kaithakkal, Kametani & Hasegawa 2020) or surface vibrations (Nakanishi, Mamori & Fukagata 2012; Nabae & Fukugata 2021) represent interesting alternatives for the control of turbulent flows.…”

Use of Surface Corrugations for Energy-Efficient Chaotic Stirring in Low Reynolds Number Flows

“…Active methods employ external body forces 17 , actuated particles 18 and various stirrers 9 with all of them requiring an external energy input. Three-dimensionality and unsteadiness do not guarantee chaos 19,20 , and not every chaotic state guarantees good stirring; either Poincaré maps or Lyapunov exponents must be used to verify whether the resulting flow is both chaos-and stirring-capable.…”