scholarly journals Diffusion or advection? Mass transfer and complex boundary layer landscapes of the brown alga Fucus vesiculosus

2017 ◽  
Vol 14 (128) ◽  
pp. 20161015 ◽  
Author(s):  
Mads Lichtenberg ◽  
Rasmus Dyrmose Nørregaard ◽  
Michael Kühl
Keyword(s):  
Boundary Layer ◽  
Mass Transfer ◽  
Three Dimensional ◽  
Fucus Vesiculosus ◽  
Pressure Gradients ◽  
Three Dimensional Mapping ◽  
Microbe Interactions ◽  
Complex Boundary ◽  
Diffusive Boundary ◽  
Set Up

The role of hyaline hairs on the thallus of brown algae in the genus Fucus is long debated and several functions have been proposed. We used a novel motorized set-up for two-dimensional and three-dimensional mapping with O 2 microsensors to investigate the spatial heterogeneity of the diffusive boundary layer (DBL) and O 2 flux around single and multiple tufts of hyaline hairs on the thallus of Fucus vesiculosus. Flow was a major determinant of DBL thickness, where higher flow decreased DBL thickness and increased O 2 flux between the algal thallus and the surrounding seawater. However, the topography of the DBL varied and did not directly follow the contour of the underlying thallus. Areas around single tufts of hyaline hairs exhibited a more complex mass-transfer boundary layer, showing both increased and decreased thickness when compared with areas over smooth thallus surfaces. Over thallus areas with several hyaline hair tufts, the overall effect was an apparent increase in the boundary layer thickness. We also found indications for advective O 2 transport driven by pressure gradients or vortex shedding downstream from dense tufts of hyaline hairs that could alleviate local mass-transfer resistances. Mass-transfer dynamics around hyaline hair tufts are thus more complex than hitherto assumed and may have important implications for algal physiology and plant–microbe interactions.

scholarly journals Diffusion or advection? Mass transfer and diffusive boundary layer landscapes of the brown alga Fucus vesiculosus

2016 ◽  
Author(s):  
Mads Lichtenberg ◽  
Rasmus Dyrmose Nøerregaard ◽  
Michael Kühl
Keyword(s):  
Boundary Layer ◽  
Mass Transfer ◽  
Fucus Vesiculosus ◽  
Pressure Gradients ◽  
Diffusive Boundary Layer ◽  
Transfer Resistance ◽  
Microbe Interactions ◽  
Diffusive Boundary ◽  
2D And 3D

AbstractThe role of hyaline hairs on the thallus of brown-algae in the genus Fucus is long debated and several functions have been proposed. We used a novel motorized setup for 2D-and 3D-mapping with O2-microsensors to investigate the spatial heterogeneity of the diffusive boundary layer (DBL) and O2 flux around single and multiple tufts of hyaline hairs on the thallus of Fucus vesiculosus. Flow was a major determinant of DBL thickness, where higher flow decreased DBL thickness and increased O2 flux between algal thallus and the surrounding seawater. However, the topography of the DBL varied and did not directly follow the contour of the underlying thallus. Areas around single tufts of hyaline hairs exhibited both increased and decreased DBL thickness as compared to areas over smooth thallus surfaces. Over thallus areas with several hyaline hair tufts, the overall effect was a local increase in the DBL thickness. We also found indications for advective O2 transport driven by pressure gradients or vortex-shedding downstream from dense tufts of hyaline hairs alleviating local mass-transfer resistance imposed by thickened DBL. Mass-transfer dynamics around hyaline hair tufts are thus more complex than hitherto assumed and may have important implications for algal physiology and plant-microbe interactions.

The Effect of a Wall Boundary Layer on Local Mass Transfer From a Cylinder in Crossflow

1984 ◽  
Vol 106 (2) ◽  
pp. 260-267 ◽  
Author(s):  
R. J. Goldstein ◽  
J. Karni
Keyword(s):  
Boundary Layer ◽  
Mass Transfer ◽  
Three Dimensional ◽  
Secondary Flows ◽  
Two Dimensional ◽  
Tunnel Wall ◽  
Wall Boundary Layer ◽  
Naphthalene Sublimation Technique ◽  
Displacement Thickness ◽  
Two Dimensional Flow

A naphthalene sublimation technique is used to determine the circumferential and longitudinal variations of mass transfer from a smooth circular cylinder in a crossflow of air. The effect of the three-dimensional secondary flows near the wall-attached ends of a cylinder is discussed. For a cylinder Reynolds number of 19000, local enhancement of the mass transfer over values in the center of the tunnel are observed up to a distance of 3.5 cylinder diameters from the tunnel wall. In a narrow span extending from the tunnel wall to about 0.066 cylinder diameters above it (about 0.75 of the mainstream boundary layer displacement thickness), increases of 90 to 700 percent over the two-dimensional flow mass transfer are measured on the front portion of the cylinder. Farther from the wall, local increases of up to 38 percent over the two-dimensional values are measured. In this region, increases of mass transfer in the rear portion of the cylinder, downstream of separation, are, in general, larger and cover a greater span than the increases in the front portion of the cylinder.

Turbulence structural changes for a three-dimensional turbulent boundary layer in a 30° bend

1994 ◽  
Vol 272 ◽  
pp. 183-210 ◽  
Author(s):  
Walter R. Schwarz ◽  
Peter Bradshaw
Keyword(s):  
Boundary Layer ◽  
Shear Stress ◽  
Turbulent Boundary Layer ◽  
Structural Changes ◽  
Three Dimensional ◽  
Energy Ratio ◽  
Pressure Gradients ◽  
Stress Energy ◽  
Cross Wire ◽  
Low Speed Wind Tunnel

A three-dimensional turbulent boundary layer (3DTBL) was generated on the floor of a low-speed wind tunnel by the imposition of a cross-stream pressure gradient using a 30° bend in the horizontal plane. The surface streamlines were deflected by as much as 22° relative to the local tunnel centreline. Downstream of the bend, the 3DTBL gradually relaxed towards a 2DTBL; this was an impulse-and-recovery experiment which focused on the outer layer. Mean velocities were measured with a three-hole yawmeter and turbulence quantities, which included the Reynolds-stress tensor and the triple products, were measured with a cross-wire hot-wire anemometer. The experiment isolated the effects of crossflow from those of adverse streamwise pressure gradients, which may have clouded interpretations of previous 3DTBL experiments. In particular, the detailed developments of the cross-stream shear stress and of the stress/energy ratio become clearer. The shear-stress vector lagged behind the velocity-gradient vector as crossflow developed; however, the two vectors became more closely aligned downstream of the bend. Reductions in the stress/energy ratio implied that crossflow made shear-stress production less efficient. Another effect of three-dimensionality was a change of sign in the vertical transport of turbulent kinetic energy by turbulence, in the inner part of the boundary layer.

Nonlinear Computational Treatment for Couple Stress Fluid Flow with Cattaneo-Christov Double Diffusion and Homogeneous-Heterogeneous Reactions

2018 ◽  
Vol 17 (1) ◽  
Author(s):  
Tasawar Hayat ◽  
Tayyaba Ayub ◽  
Taseer Muhammad ◽  
Bashir Ahmad
Keyword(s):  
Boundary Layer ◽  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Couple Stress ◽  
Three Dimensional ◽  
Double Diffusion ◽  
Convergent Series ◽  
Heterogeneous Reactions ◽  
Optimal Homotopy Analysis Method ◽  
Transfer Rates

Abstract This paper addresses three-dimensional (3D) flow of couple stress material with Cattaneo-Christov double diffusion and homogeneous-heterogeneous reactions. A linear bi-directional stretchable surface is used to generate the flow. Thermal and concentration diffusions are considered by introducing Cattaneo-Christov heat and mass fluxes. Equal diffusion coefficients are considered for both auto catalyst and reactants. Boundary layer approach is used to simplify the governing system of partial differential equations. Suitable relations are used to nondimensionalize the boundary layer expressions. The valid convergent series solution are established by means of optimal homotopy analysis method (OHAM). The role of various pertinent parameters on the solutions are investigated through graphs. Moreover skin friction coefficients and heat and mass transfer rates are computed and analyzed. It is observed that heat and mass transfer rates are higher for larger thermal and concentration relaxation parameters.

The Thurston Rotor Cowl for Air-Cooled Engines

1935 ◽  
Vol 39 (293) ◽  
pp. 445-447
Author(s):  
A. P. Thurston
Keyword(s):  
Boundary Layer ◽  
Radial Flow ◽  
Air Flow ◽  
Cooling Effect ◽  
Pressure Gradients ◽  
Aircraft Engines ◽  
Undesirable Effect ◽  
Forward Flow ◽  
Set Up ◽  
Horse Power

One of the main problems in connection with the development of air-cooled engines appears to consist in securing adequate cooling without increasing the head resistance above that of corresponding water-cooled engines.This problem particularly applies to large air-cooled engines which are limited in size by cooling difficulties. Air-cooled engines for windmill planes and helicopters for alternate slow and fast flying present a further problem, because such aircraft engines will be required to develop maximum horse-power when the speed of translation is lowest.The airflow over the nose of a bulky body, such as that of an aeroplane, diverges radially in every direction from its axis. Such radial flow tends to overshoot laterally, at its core, the periphery of the engine or other obstruction and so depart from the contour thereof, with the result that a considerable turbulence is set up. Such turbulence has also the undesirable effect of causing a reversal of the pressure gradients, and a corresponding reversed or forward flow of air, in the boundary layer behind the engine, thereby creating a ” dead “ area or areas and so considerably reducing the cooling effect of the general air flow and increasing the turbulence.

Effect of Adverse Pressure Gradients on Turbulent Boundary Layers in Axisymmetric Conduits

1957 ◽  
Vol 24 (2) ◽  
pp. 191-196
Author(s):  
J. M. Robertson ◽  
J. W. Holl
Keyword(s):  
Boundary Layer ◽  
Flow Parameter ◽  
Three Dimensional ◽  
Turbulent Boundary Layers ◽  
Pressure Gradients ◽  
Two Dimensional ◽  
Flow Conditions ◽  
Straight Pipe ◽  
Outer Flow ◽  
Dimensional Boundary

Abstract The development of the three-dimensional boundary layer in a diffuser with several discharge arrangements has been studied for air flow, in continuation of the work of Uram (1). The flow conditions in a diffuser when followed by a straight pipe, an additional length of the diffuser, or a jet, are compared. Extension of the method of analysis developed by Ross for two-dimensional layers is presented. In some cases the use of three-dimensionally defined parameters leads to different results. Ross’s (2) unique outer-flow parameter is found to be no longer satisfactory. Other outer parameters are presented as possible substitutes.

A nonlinear, asymptotic investigation of the stationary modes of instability of the three-dimensional boundary layer on a rotating disc

1987 ◽  
Vol 413 (1845) ◽  
pp. 497-513 ◽  
Keyword(s):  
Boundary Layer ◽  
Three Dimensional ◽  
Nonlinear Effects ◽  
Finite Amplitude ◽  
Neutral Stability ◽  
Lower Branch ◽  
Rotating Disc ◽  
Dimensional Boundary ◽  
High Reynolds ◽  
Set Up

There exist two types of stationary instability of the flow over a rotating disc corresponding to the upper, inviscid mode and the lower-branch mode, which has a triple-deck structure, of the neutral stability curve. The linear problem has been investigated by P. Hall ( Proc. R. Soc. Lond. A 406, 93-106 (1986)) and the asymptotic structure of the wavenumber and orientation of these modes has been obtained. Here, a nonlinear investigation of high Reynolds number, stationary instabilities in the three-dimensional boundary layer on a rotating disc is given for the lower branch mode. By considering nonlinear effects and following the framework set up by Hall, asymptotic solutions are obtained that enable the finite amplitude growth of a disturbance close to the neutral location to be described.

scholarly journals Pattern formation and coarsening dynamics in three-dimensional convective mixing in porous media

2013 ◽  
Vol 371 (2004) ◽  
pp. 20120355 ◽  
Author(s):  
Xiaojing Fu ◽  
Luis Cueto-Felgueroso ◽  
Ruben Juanes
Keyword(s):  
Boundary Layer ◽  
Pattern Formation ◽  
Cellular Network ◽  
Gravitational Instability ◽  
Three Dimensional ◽  
Concentration Field ◽  
Convective Mixing ◽  
Long Term Storage ◽  
Diffusive Boundary ◽  
Dimensional Simulation

Geological carbon dioxide (CO 2 ) sequestration entails capturing and injecting CO 2 into deep saline aquifers for long-term storage. The injected CO 2 partially dissolves in groundwater to form a mixture that is denser than the initial groundwater. The local increase in density triggers a gravitational instability at the boundary layer that further develops into columnar plumes of CO 2 -rich brine, a process that greatly accelerates solubility trapping of the CO 2 . Here, we investigate the pattern-formation aspects of convective mixing during geological CO 2 sequestration by means of high-resolution three-dimensional simulation. We find that the CO 2 concentration field self-organizes as a cellular network structure in the diffusive boundary layer at the top boundary. By studying the statistics of the cellular network, we identify various regimes of finger coarsening over time, the existence of a non-equilibrium stationary state, and a universal scaling of three-dimensional convective mixing.

Sign in / Sign up

Export Citation Format

Share Document