Effects of polymer additives in the bulk of turbulent thermal convection
arXiv:1511.03822 · doi:10.1017/jfm.2015.618
Abstract
We present experimental evidence that a minute amount of polymer additives can significantly enhance heat transport in the bulk region of turbulent thermal convection. The effects of polymer additives are found to be the \textit{suppression} of turbulent background fluctuations that give rise to incoherent heat fluxes that make no net contribution to heat transport, and at the same time to \textit{increase} the coherency of temperature and velocity fields. The suppression of small-scale turbulent fluctuations leads to more coherent thermal plumes that result in the heat transport enhancement. The fact that polymer additives can increase the coherency of thermal plumes is supported by the measurements of a number of local quantities, such as the extracted plume amplitude and width, the velocity autocorrelation functions and the velocity-temperature cross-correlation coefficient. The results from local measurements also suggest the existence of a threshold value for the polymer concentration, only above which can significant modification of the plume coherent properties and enhancement of the local heat flux be observed. Estimation of the plume emission rate suggests that the second effect of polymer additives is to stabilize the thermal boundary layers.
arXiv comment8 figures, 11 pages
References in corpus (11)
- Large scale dynamics in turbulent Rayleigh-Benard convection
- Colloquium: Theory of Drag Reduction by Polymers in Wall Bounded Turbulence
- The ultimate state of thermal convection
- Rayleigh and Prandtl number scaling in the bulk of Rayleigh-Benard turbulence
- Measured Instantaneous Viscous Boundary Layer in Turbulent Rayleigh-Bénard Convection
- Prandtl-Blasius temperature and velocity boundary layer profiles in turbulent Rayleigh-Bénard convection
- Effect of a polymer additive on heat transport in turbulent Rayleigh-Bénard convection
- Extraction of Plumes in Turbulent Thermal Convection
- Polymer heat transport enhancement in thermal convection: the case of Rayleigh-Taylor turbulence
- Fluid Acceleration in the Bulk Turbulence of Dilute Polymer Solutions
- Heat transport by laminar boundary layer flow with polymers
Cited by in corpus (4)
- Polymers in Fluid Flows
- Turbulent thermal convection over rough plates with varying roughness geometries
- Experimental observation of the elastic range scaling in turbulent flow with polymer additives
- Effect of Prandtl number on heat transport enhancement in Rayleigh-Bénard convection under geometrical confinement