Patterns and Predictors of Small Mammal Phylogenetic and Functional Diversity in Contrasting Elevational Gradients in Kenya

Mountains of the Afrotropics are global biodiversity hotspots and centers of speciation and endemism; however, very few studies have focused on the phylogenetic and functional dimensions of Afromontane small mammals. We investigated the patterns and mechanisms of small mammal phylogenetic and functional diversity and assembly along elevational gradients in Mount Kenya, the second highest mountain in Africa, and a contrasting low mountain range, Chyulu Hills. We sampled 24 200-m interval transects in both sites; 18 in Mt. Kenya (9 each in the windward side, Chogoria, and the leeward side, Sirimon) and 6 in Chyulu. We extracted the mitochondrial Cytochrome b gene to reconstruct a time-calibrated species tree for estimating phylogenetic diversity indices [phylogenetic richness (PD), mean nearest taxon distance (PDMNTD), and nearest taxon index (PDNTI)]. A functional trait data set was compiled from the field-recorded measurements and published data sets for estimating functional diversity indices [functional richness (FD), mean nearest taxon distance (FDMNTD), and nearest taxon index (FDNTI)]. Several environmental variables representing water-energy availability, primary habitat productivity, and topographic heterogeneity were used to estimate the predictive power of abiotic conditions on diversity variances using generalized linear and generalized additive regression models. The PD and FD peaked around mid-elevations in Mt. Kenya, unimodally increased or decreased in Chogoria and Sirimon, and monotonically increased in Chyulu. The divergence and community structure indices—PDMNTD, FDMNTD, and PDNTI and FDNTI—were relatively weakly associated with elevation. Overall, the tendency of assemblages to be phylogenetically and functionally closely related than expected by chance decreased with elevation in Mt. Kenya but increased in Chyulu. Across the indices, the annual precipitation and topographic ruggedness were the strongest predictors in Mt. Kenya, evapotranspiration and temperature seasonality were the strongest predictors in Chyulu, while temperature seasonality and terrain ruggedness overlapped as the strongest predictors in Chogoria and Sirimon in addition to annual precipitation in the latter and normalized difference vegetation index in the former. The observed contrasting trends in diversity distribution and the strongest predictors between elevational gradients are integral to the sustainable management of the high faunal biodiversity in tropical Afromontane ecosystems.

Effect of latent heat release on mountain waves in a sheared mean flow

ABSTRACT. The effect of latent heat release on windward side of the mountain due to precipitation over the mountain waves has been studied assuming wind speed changing with respect to height. A single profile based on actual Peshawar data has been considered for the analysis. A thin level of heating has been chosen at medium level for the purpose of study. For non-hydrostatic case it is observed that in non-precipitation case when balanced heating/cooling takes place on the windward/leeward side or the mountain the effect of heating is negligibly small. However, for precipitation case downward displacement on the windward side, just above the level of heating. is obvious. Interference with the upstream current by the waves, produced due to elevated thermal forcing and reflected from the around surface is attributed to this phenomenon. Increase in the wave amplitude on the lee-side of the mountain as compared to non-precipitating case is also found. It is also revealed that higher the level or heating lesser the amplitude of the induced disturbance. 4.5 km agl is the level which is maximum affected by heating in general. For large and shallow mountainous terrains. hydrostatic solutions have been produced for three different levels of heating for sheared flow, Streamlines have been drawn. On comparison with no shear case, it may be inferred that shear effect is opposite to that due to thermal forcing.

Influence of Gas Flooding Pressure on Groundwater Flow during Oil Shale In Situ Exploitation

In order to weaken the influence of external groundwater on in situ pyrolysis exploitation, the flow characteristics of groundwater were studied according to the oil shale reservoir characteristics of Qingshankou Formation in Songliao Basin, China. In addition, the parameters of marginal gas flooding for water-stopping were optimized. Taking a one-to-one pattern and a five-spot pattern as examples, the characteristics of groundwater flow under the in situ process were studied. Under the one-to-one pattern, the external groundwater flows into the production well from the low-pressure side, and the water yield was basically stable at 1000 kg/d. In the five-spot pattern, the groundwater can flow into the production wells directly from the windward side, and the water yield of the production well on the leeward side mainly comes from the desaturated zone; the water yield of each production well remains at a high level. By setting water-stopping wells around the production well and keeping the gas flooding pressure slightly higher than the production well, the water yield of the production well can be reduced and stabilized within 100 kg/d under gas flooding pressures of 3 and 5 MPa. However, the gas yield of the production well slightly decreased when the gas flooding pressure reduced from 5 to 3 MPa. Therefore, the gas flooding pressure of water-stopping wells shall be determined in combination with the water yield and gas yield, so as to achieve the best process effect. It is expected that the results will provide technical support for large-scale oil shale in situ pyrolysis exploitation.

Wind Environment Study of High-rise Residential Building by using Multiple Computational Tools

<p>Wind environment is a key element of sustainable design of architecture. Concerning major trends of climate changes and urbanizations, this research aims to study the relationships between the influences on wind environments and variables related to forms and configurations of contemporary high-rise residential buildings. A novel methodology consisting of parametric design, CFD simulation, and analysis is developed by integrating multiple computational tools, and the evaluation criteria. The integration provides abundant functions and an efficient modelling-simulation-analysis solution for iterative comparison studies. By using a parametric modelling method, building models can be created automatically to help in mesh generation for CFD simulations; the actual influenced areas with different wind velocity ranges can be calculated and compared quantitatively through the calculations of wind-velocity magnitudes from simulation results, at each pixel location on a rendered section. Based on the architectural morphology of Building-Unit Forms (BUFs) and Building-Cluster Configurations (BCCs) in an area classified in China as a Hot-Summer and Cold-Winter Area (HSCWA), the parametric design sets up a bridge between building variables and CFD simulations. A series of representative BUFs and BCCs of high-rise residential buildings are designed for CFD simulations by establishing parametric design system based on the building categorization study. In the wind environment studies, influences of buildings are evaluated based on the wind-velocity magnitudes according to the criteria. The trends of influences can be studied through iterative analysis of several cases with different variables. The mechanisms are illustrated through the air-pressure magnitudes and the wind-flow streamlines. In the wind environment studies of BUFs, relationships between influences on wind environments and building variables of three representative BUFs are studied, including square form, rectangular form, and ‘T’ form. The results of the BUFs studies can be summarized: (1) the influences on wind environments increase as the height and windward length are increased, because more winds are obstructed by the increasing windward surface; (2) the influences on wind environments decrease as the ratio of length and width is increased before the ratio reaches a particular value, because influenced air-pressure area is decreased; (3) the influences on the wind environments decrease as the bulge-part sizes of the ‘T’-form buildings increase, because the increases of bulge-part sizes help to divide winds and lead them to flow around the buildings; (4) the outdoor ventilation is improved as the rotation angle increases, because the non-vertical windward surface promotes the wind flow. In the wind environment studies of BCCs, relationships between influences on wind environments and building variables of three representative BCCs are studied, including scattered configuration, linear configuration, and curvilinear configuration. Results of the BCCs studies can be summarized: (1) the outdoor ventilation of scattered configuration is the best, because it is relatively easy for winds to flow around the scattered building units; (2) the outdoor ventilation can be improved as the longitudinal distance and staggered distance are increased, because the larger building interval promotes winds to flow through the building cluster; (3) for curvilinear configuration, the convex surface on the windward side can promote the wind flow, and the concave surface on the windward side can obstruct the wind flow. The results of the BUFs studies and the BCCs studies all show that the increases of the windward projective areas of buildings can increase the influences on wind environments, because more winds are obstructed. Therefore, the relationships between the influences on wind environments and the building variables of the BUFs and BCCs can be discovered, which can give information to the optimization of wind environments. In summary, the thesis presents a challenging and significant research that contributes original knowledge for wind environment studies in the urban micro climate. And the knowledge is universal and applicable to the practical design projects and also beneficial to the sustainability.</p>

Wind Environment Study of High-rise Residential Building by using Multiple Computational Tools

<p>Wind environment is a key element of sustainable design of architecture. Concerning major trends of climate changes and urbanizations, this research aims to study the relationships between the influences on wind environments and variables related to forms and configurations of contemporary high-rise residential buildings. A novel methodology consisting of parametric design, CFD simulation, and analysis is developed by integrating multiple computational tools, and the evaluation criteria. The integration provides abundant functions and an efficient modelling-simulation-analysis solution for iterative comparison studies. By using a parametric modelling method, building models can be created automatically to help in mesh generation for CFD simulations; the actual influenced areas with different wind velocity ranges can be calculated and compared quantitatively through the calculations of wind-velocity magnitudes from simulation results, at each pixel location on a rendered section. Based on the architectural morphology of Building-Unit Forms (BUFs) and Building-Cluster Configurations (BCCs) in an area classified in China as a Hot-Summer and Cold-Winter Area (HSCWA), the parametric design sets up a bridge between building variables and CFD simulations. A series of representative BUFs and BCCs of high-rise residential buildings are designed for CFD simulations by establishing parametric design system based on the building categorization study. In the wind environment studies, influences of buildings are evaluated based on the wind-velocity magnitudes according to the criteria. The trends of influences can be studied through iterative analysis of several cases with different variables. The mechanisms are illustrated through the air-pressure magnitudes and the wind-flow streamlines. In the wind environment studies of BUFs, relationships between influences on wind environments and building variables of three representative BUFs are studied, including square form, rectangular form, and ‘T’ form. The results of the BUFs studies can be summarized: (1) the influences on wind environments increase as the height and windward length are increased, because more winds are obstructed by the increasing windward surface; (2) the influences on wind environments decrease as the ratio of length and width is increased before the ratio reaches a particular value, because influenced air-pressure area is decreased; (3) the influences on the wind environments decrease as the bulge-part sizes of the ‘T’-form buildings increase, because the increases of bulge-part sizes help to divide winds and lead them to flow around the buildings; (4) the outdoor ventilation is improved as the rotation angle increases, because the non-vertical windward surface promotes the wind flow. In the wind environment studies of BCCs, relationships between influences on wind environments and building variables of three representative BCCs are studied, including scattered configuration, linear configuration, and curvilinear configuration. Results of the BCCs studies can be summarized: (1) the outdoor ventilation of scattered configuration is the best, because it is relatively easy for winds to flow around the scattered building units; (2) the outdoor ventilation can be improved as the longitudinal distance and staggered distance are increased, because the larger building interval promotes winds to flow through the building cluster; (3) for curvilinear configuration, the convex surface on the windward side can promote the wind flow, and the concave surface on the windward side can obstruct the wind flow. The results of the BUFs studies and the BCCs studies all show that the increases of the windward projective areas of buildings can increase the influences on wind environments, because more winds are obstructed. Therefore, the relationships between the influences on wind environments and the building variables of the BUFs and BCCs can be discovered, which can give information to the optimization of wind environments. In summary, the thesis presents a challenging and significant research that contributes original knowledge for wind environment studies in the urban micro climate. And the knowledge is universal and applicable to the practical design projects and also beneficial to the sustainability.</p>

Numerical Analysis on the Crosswind Influence Around a Generic Train Moving on Different Bridge Configurations

In this article, a numerical approach is applied to study the flow regimes surround a generic train model travelling on different bridge configurations under the influence of crosswind. The bridge is varies based on the different geometry of the bridge girder. The crosswind flow angle (Ψ) is varied from 0° to 90°. The incompressible flow around the train was resolved by utilizing the Reynolds-averaged Navier-Stokes (RANS) equations combined with the SST k-ω turbulence model. The Reynolds number used, based on the height of the train and the freestream velocity, is 3.7 × 105. In the results, it was found that variations of the crosswind flow angles produced different flow regimes. Two unique flow regimes appear, representing (i) slender body flow behaviour at a smaller range of Ψ (i.e. Ψ ≤ 45°) and (ii) bluff body flow behaviour at a higher range of Ψ (i.e. Ψ ≥ 60°). As the geometries of the bridge girder were varied, the bridge with the wedge girder showed the worst aerodynamic properties with both important aerodynamic loads (i.e. side force and rolling moment), followed by the triangular girder and the rectangular girder. This was due to the flow separation on the windward side and flow structure formation on the leeward side, both of which are majorly influenced by the flow that moved from the top and below of the bridge structures.

Intensification of non-uniformity in convergent near-conical hypersonic flow

The inevitable formation of a Mach disk at the central axis of a convergent conical shock wave may suffer from fundamental changes when the flow deviates from the axisymmetric condition. In this paper, the behaviours of near-conical shocks, which are generated by a circular ring wedge of $10^{\circ }$ at typical angles of attack (AoAs), are investigated at a free stream Mach number of 6 in a shock tunnel. To reveal the characteristics and mechanism of the flow, numerical analyses are carried out under the same conditions. The results indicate that when the flow deviates from axial symmetry, the circumferential non-uniformity is remarkably intensified as the shock converges downstream. The converging centre shifts against the inclination of the incoming flow and moves to the leeward side. For a sufficiently small AoA, the formation of a Mach disk remains similar to that in the axisymmetric case, although the Mach disk shrinks in size and is slightly flattened. As the circumferential non-uniformity of the shock increases at an AoA of approximately $3^{\circ }$ , a pair of kinks separate the shock surface into two discontinuous segments with the stronger shock segment on the windward side and the weaker shock segment on the leeward side. When the AoA increases further, the shrinkage of the Mach disk continuously occurs, and the Mach disk is eventually replaced by a regular reflection. The discontinuity of a convergent shock with flattening on the separated shock segments and the insufficient strength increase during the subsequent convergence are responsible for the appearance of regular reflection.

Conceptual Design and Hydrodynamic Performance of a Modular Hybrid Floating Foundation

The comprehensive utilization of offshore renewable energies is an effective way to solve the intermittency and variability of power supply. This paper aims to present a hybrid floating system (HFS) based on a modular buoyancy-distributed floating foundation (BDFF) that can be equipped with a horizontal-axis wind turbine, solar panels, and wave energy converters (WEC). A simplified test model with a Froude scale ratio of 1/10 is employed to perform the experiments in a deep-water basin to validate the numerical results computed from the code program ANSYS AQWA based on the potential flow theory. The Response Amplitude Operators (RAOs) under regular waves are compared to evaluate the hydrodynamic performance. There is a good agreement in the surge, pitch, and heave RAOs for experiments and the numerical simulation, with a maximum of 6.45 degrees per meter for the pitch motion. Furthermore, the mooring tensions in the time domain are analyzed under different wave conditions.The tension RAOs from simulations are slightly higher than those from measurements with a maximum value at the period of 3.416 s. The mooring line on the windward side has a more considerable mooring tension that is far less than the allowable tensile strength, especially under the wave height of 2 m and the wave period of 2.873 s. The influence of loaded weight representing solar panels is weak, and the impact of winds is acceptable, as the platform deviates 1.3 degrees from the equilibrium state under the test wind speed. Eventually, the effect of irregular waves on the HFS is presented with the critical parameters of mooring tension and pitch motion. The results show that the HFS has a good motion performance.

Semi-Permanent Zones of Radar Radial Shear within the Planetary Boundary Layer: Observations and Effects on High Intensity Precipitation in the Wider Auckland region, New Zealand

<p>This study investigates the role of mechanical forcing within the boundary layer in enhancing low-level precipitation and initiating/intensifying convective precipitation during cases of high intensity precipitation in the wider Auckland region, New Zealand. Eight cases, that occurred between 2001 and 2008 have been investigated. All cases were observed to be strongly dynamically forced, resulting from the passage of mid-latitude cyclones. These features were observed to be centred mainly to the north and west of the study area, with surface winds from the northeast quadrant over the wider Auckland region. Radar imagery is characterised by regions of both convective and stratiform precipitation for all the cases investigated; areas of convection are often observed to be embedded in areas of larger scale precipitation. These cases were subdivided into eleven heavy precipitation events. Nine of these events were subject to further investigation. Environmental conditions during these events were characterised by steady low-level winds from the northeast quadrant, weak to moderate convective instability, with 0-3km wind shear indicating a high level of directional shear in the lower atmosphere. To investigate mechanical forcing in the boundary layer, low-level Doppler velocity and reflectivity fields measured by the Mt Tamahunga radar, were examined. These data revealed mesoscale structures of the Doppler velocity field not previously documented in this region. Mechanical forcing was identified by the presence of mesoscale zones of radar radial shear, resulting from horizonal convergence and/or zones of horizontal shear. These features were observed to be semi-permanent on the windward side of Little Barrier and Great Barrier islands, the windward side of the Coromandel ranges, and along the west coast of the Auckland region. Further, zones of semi-permanent radar radial shear were observed to extend downstream (lee side) of Mt Moehau and Great Barrier, Little Barrier and Taranga islands in the Hauraki Gulf. These features have not been documented previously for this study area. The features, observed downstream of each obstacle, were characterised by a long thin low velocity zone present in PPI images of radar radial velocity and were bounded by the above mentioned shear zones. Further, these features were aligned parallel to the surface wind direction, with widths approximately equal to the diameter of the obstacle and extended up to 57km downstream of each obstacle. These features are consistent with characteristics of mountain wakes described in the literature. A partitioning algorithm was calibrated to identify the convective and stratiform components of the radar reflectivity field. This algorithm was applied to reflectivity data for each heavy precipitation event. Local maxima in the frequency of low-level enhanced precipitation were observed in the vicinity of topographic features such as the Coromandel Peninsula and Mt Tamahunga, in addition to the observed location of wakes in the lee of Great Barrier and Little Barrier Island. Finally, the relationship between mountain wakes observed in the Hauraki Gulf and low-level precipitation enhancement was examined. Investigations showed that when large scale areas of precipitation interacted with these wakes, in some cases convective precipitation was observed to be initiated or intensified. However, the observed areas of enhancement were observed to be short lived and shallow, reaching heights below the radar bright band at [approximately ]3.5 km.</p>

Semi-Permanent Zones of Radar Radial Shear within the Planetary Boundary Layer: Observations and Effects on High Intensity Precipitation in the Wider Auckland region, New Zealand

<p>This study investigates the role of mechanical forcing within the boundary layer in enhancing low-level precipitation and initiating/intensifying convective precipitation during cases of high intensity precipitation in the wider Auckland region, New Zealand. Eight cases, that occurred between 2001 and 2008 have been investigated. All cases were observed to be strongly dynamically forced, resulting from the passage of mid-latitude cyclones. These features were observed to be centred mainly to the north and west of the study area, with surface winds from the northeast quadrant over the wider Auckland region. Radar imagery is characterised by regions of both convective and stratiform precipitation for all the cases investigated; areas of convection are often observed to be embedded in areas of larger scale precipitation. These cases were subdivided into eleven heavy precipitation events. Nine of these events were subject to further investigation. Environmental conditions during these events were characterised by steady low-level winds from the northeast quadrant, weak to moderate convective instability, with 0-3km wind shear indicating a high level of directional shear in the lower atmosphere. To investigate mechanical forcing in the boundary layer, low-level Doppler velocity and reflectivity fields measured by the Mt Tamahunga radar, were examined. These data revealed mesoscale structures of the Doppler velocity field not previously documented in this region. Mechanical forcing was identified by the presence of mesoscale zones of radar radial shear, resulting from horizonal convergence and/or zones of horizontal shear. These features were observed to be semi-permanent on the windward side of Little Barrier and Great Barrier islands, the windward side of the Coromandel ranges, and along the west coast of the Auckland region. Further, zones of semi-permanent radar radial shear were observed to extend downstream (lee side) of Mt Moehau and Great Barrier, Little Barrier and Taranga islands in the Hauraki Gulf. These features have not been documented previously for this study area. The features, observed downstream of each obstacle, were characterised by a long thin low velocity zone present in PPI images of radar radial velocity and were bounded by the above mentioned shear zones. Further, these features were aligned parallel to the surface wind direction, with widths approximately equal to the diameter of the obstacle and extended up to 57km downstream of each obstacle. These features are consistent with characteristics of mountain wakes described in the literature. A partitioning algorithm was calibrated to identify the convective and stratiform components of the radar reflectivity field. This algorithm was applied to reflectivity data for each heavy precipitation event. Local maxima in the frequency of low-level enhanced precipitation were observed in the vicinity of topographic features such as the Coromandel Peninsula and Mt Tamahunga, in addition to the observed location of wakes in the lee of Great Barrier and Little Barrier Island. Finally, the relationship between mountain wakes observed in the Hauraki Gulf and low-level precipitation enhancement was examined. Investigations showed that when large scale areas of precipitation interacted with these wakes, in some cases convective precipitation was observed to be initiated or intensified. However, the observed areas of enhancement were observed to be short lived and shallow, reaching heights below the radar bright band at [approximately ]3.5 km.</p>