Shelf Transport Pathways Adjacent to the East Australian Current Reveal Sources of Productivity for Coastal Reefs

The region where the East Australian Current (EAC) separates from the coast is dynamic and the shelf circulation is impacted by the interplay of the western boundary current and its eddy field with the coastal ocean. This interaction can drive upwelling, retention or export. Hence understanding the connection between offshore waters and the inner shelf is needed as it influences the productivity potential of valuable coastal rocky reefs. Near urban centres, artificial reefs enhance fishing opportunities in coastal waters, however these reefs are located without consideration of the productivity potential of adjacent waters. Here we identify three dominant modes of mesoscale circulation in the EAC separation region (~31.5−34.5°S); the ‘EAC mode’ which dominates the flow in the poleward direction, and two eddy modes, the ‘EAC eddy mode’ and the ‘Eddy dipole mode’, which are determined by the configuration of a cyclonic and anticyclonic eddy and the relationship with the separated EAC jet. We use a Lagrangian approach to reveal the transport pathways across the shelf to understand the impact of the mesoscale circulation modes and to explore the productivity potential of the coastal waters. We investigate the origin (position and depth) of the water that arrives at the inner-mid shelf over a 21-day period (the plankton productivity timescale). We show that the proportion of water that is upwelled from below the euphotic zone varies spatially, and with each mesoscale circulation mode. Additionally, shelf transport timescales and pathways are also impacted by the mesoscale circulation. The highest proportion of upwelling (70%) occurs upstream of 32.5°S, associated with the EAC jet separation, with vertical displacements of 70–120 m. From 33 to 33.5°S, water comes from offshore above the euphotic layer, and shelf transport timescales are longest. The region of highest retention over the inner shelf is immediately downstream of the EAC separation region. The position of the EAC jet and the location of the cyclonic eddy determines the variability in shelf-ocean interactions and the productivity of shelf waters. These results are useful for understanding productivity of temperate rocky reefs in general and specifically for fisheries enhancements along an increasingly urbanised coast.

Flow and heat transfer in the separation region behind a backward-facing step with convergently mounted plates of longitudinal vortex generator

The paper presents the results of an experimental study of the dynamics of separated flow and heat transfer behind a backward-facing step when using longitudinal vortex generators (LVGs) at an angle of -30º at Re = 4000. Longitudinal vortex generators represent a pair of plates with a height of 6 mm, located symmetrically relative to the flow. Along with the average values, the pulsation characteristics of the flow are considered. The thermohydraulic efficiency was estimated by the found dynamic and thermal characteristics.

Mathematical modeling of contact interaction of two electroelastic half-spaces (without electrode coating of surfaces) in the presence of a hard disk-like inclusion between them and pressure in the area of separation

Based on the use of a rigorous mathematical model that takes into account the connectivity of force and electric fields in electroelastic bodies, the contact interaction of two piezoelectric transversely isotropic half-spaces with different properties under compression (in the presence of a hard disk-shaped inclusion between them and pressure in the material separation region) was studied. The solution to the problem is obtained by representing the general solution of the static equations of the electroelasticity for a transversely isotropic body in terms of harmonic functions, followed by the construction of the boundary value problem of the electroelasticity to the consideration of the integral equation and the expansion of the desired function in a small parameter. As a special case from the constructed analytical expressions, the main parameters of the contact for two elastic transversely isotropic and isotropic half-spaces (with the inclusion between them and pressure in the separation region) are implied. Numerical results were obtained. The influence was studied of the electroelastic properties of half-spaces, the geometric dimensions of the inclusion, and loads on the parameters of the contact interaction of electroelastic bodies.

Features of air flow and heat transfer control behind a backward-facing step using a vortex generator pair

The paper presents experimental results on the study of flow dynamics and heat transfer in the separation region behind the backward-facing step with longitudinal vortex generators (VG) installed at an angle to the flow of 30° at Re = 4000. The VG installation reduces the recirculation region and the induced longitudinal vortices and rearranges the flow structure in the separation region. The influence of a VG on the local and average thermal characteristics behind the backward-facing step is investigated and their thermohydraulic efficiency is estimated.

Effect of the Reynolds Number and Clearance Flow on the Aerodynamic Characteristics of a New Variable Inlet Guide Vane

Recently, a new type of low-loss variable inlet guide vane (VIGV) was proposed for improving a compressor’s performance under off-design conditions. To provide more information for applications, this work investigated the effect of the Reynolds number and clearance flow on the aerodynamic characteristics of this new type of VIGV. The performance and flow field of two representative airfoils with different chord Reynolds numbers were studied with the widely used commercial software ANSYS CFX after validation was completed. Calculations indicate that, with the decrease in the Reynolds number Rec, the airfoil loss coefficient ω and deviation δ first increase slightly and then entered a high growth rate in a low range of Rec. Afterwards, a detailed boundary-layer analysis was conducted to reveal the flow mechanism for the airfoil performance degradation with a low Reynolds number. For the design point, it is the appearance and extension of the separation region on the rear portion; for the maximum incidence point, it is the increase in the length and height of the separation region on the former portion. The three-dimensional VIGV research confirms the Reynolds number effect on airfoils. Furthermore, the clearance leakage flow forms a strong stream-wise vortex by injection into the mainflow, resulting in a high total-pressure loss and under-turning in the endwall region, which shows the potential benefits of seal treatment.

Global Visualization of Compressible Swept Convex-Corner Flow Using Pressure-Sensitive Paint

This study used pressure-sensitive paint (PSP) and determined the surface pressure distributions for a compressible swept convex-corner flow. The freestream Mach numbers were 0.64 and 0.83. The convex-corner angle and swept angle were, respectively, 10–17° and 5–15°. Expansion and compression near the corner apex were clearly visualized. For the test case of shock-induced boundary layer separation, there were greater spanwise pressure gradient and curved shocks. The acquired PSP data agree with the experimental data measured using the Kulite pressure transducers for a subsonic expansion flow. For a transonic expansion flow, the discrepancy was significant. The assumption of a constant recovery factor is not valid in the separation region, and temperature correction for PSP measurements is required.

An insulator becomes a conductor under the quantised, critical field: (The Insuductor)

In the solid state physics, one could imagine that if the lattice constant (a) is increased, then what will be the consequences? According to band theory, as long as one starts with a half-filled band (i.e. one electron per unit cell), then, the system will not change but will remain metallic no matter how the atoms were pulled far apart, that will lead to an absurd. Where, at very large lattice separation, there exists a limit, where the conductor becomes just an array of atoms which implies the delocalisation of the electrons at each atom around their nucleus, Hence, the conductor in this limit tends to be an insulator. The big question now is (Why for large values of the lattice constant that array must be an insulator?).At very small lattice separation, the quantum mechanical tunnelling occurs with perfect transmission coefficient, hence, with perfect delocalisation, which ensures the case of a conductor. At very large lattice separation, the quantum mechanical tunnelling is forbidden with zero transmission coefficient, hence, with zero delocalisation. Hence, the localisation coefficient is perfect, and indeed this is the case of an insulator. At very large lattice separation, the conductor becomes an insulator. Applying the negative, critical potential on the lattice separation region allows the delocalisation coefficient to be perfect due to the qunatisation of the critical potential, then, an insulator becomes a conductor. Therefore, (The Insuductor) is an insulator which converted into a conductor under the quantised, critical field.

Combined Flow Control of Positively Bowed Blade and Vortex Generator Jet on a Compressor Cascade

A combined flow control method based on positively bowed blade and endwall vortex generator jet (VGJ) was performed to a compressor cascade under three kinds of inlet conditions. The results show that the endwall VGJ can further decrease the total losses in positively bowed cascades. At 0° incidence with zero inlet boundary layer, the separation type in the positively bowed blade is open, with the VGJ, the loss reduction is 2.7 %. As the inlet boundary layer thickens at 0° incidence, the separation region increases with the separation type keeping unchanged, the loss reduction increasing to 11.73 %. As the incidence rises to +7° with zero inlet boundary layer, the separation type converts into closed and the flow separation is the severest in the three cases, with the VGJ, however, the loss reduction is just 7.4 %, which means that the control effect of endwall VGJ not only depends on the size of separation region but also relies on the type of separation mode. If the separation type is open, as the size of separation region expands, the control effectiveness of endwall VGJ increases; if the separation type converts into closed with the further aggravation of flow field, that control effect will decrease.