Effects of Bypass Flow Distribution on Cold Flow Characteristics of Integrated Afterburner

Integrated design is a trend in the development of afterburners, and the distribution of cold flow is directly related to their flow field characteristics, combustion organization, and the cooling effect of components. Numerical simulations were performed to illustrate the effects of bypass flow distribution on the flow distribution, mixing characteristics, and cooling efficiency of the components by varying the cooling flow path structure parameters. Within the range of parameters in this study, it can be indicated that with the increase of heat shield inlet height and afterburner annulus height, the total pressure recovery coefficient along the path increased accordingly, and the increasing rate at the afterburner outlet is 1.12% and 1.19%, respectively. The average cooling efficiency of radial flameholder, circumferential flameholder, and fuel injector all decrease, but the rate of decrease varies slightly depending on the location of the components. The increase of heat shield inlet height would reduce thermal mixing efficiency by approximately 5.4% at the afterburner outlet, and the increase of afterburner annular height would increase about 2.9%.

Residence time distribution studies on recycle reactor with recirculation

Residence time distribution (RTD) experiments provide very important information about the performance of reactors. In the present work, RTD experiments were performed with varying recycle and recirculation rates to see their effect on mean residence time (MRT), flow bypassing and stagnant volume in the reactor. A computer program was developed to solve the model equations using fourth-order Runge–Kutta method. A low bypass flow (<5%) was observed from the experimental RTD curves obtained at different operating conditions. A change in the MRT from 1.2 to 1.8 h was observed at different recycle and recirculation rates. At maximum recycle and maximum recirculation, in the study ranges, a 37% stagnant volume (with exchange) was predicted. In the absence of recycle and recirculation, a 53% stagnant volume (with exchange) was predicted corresponding to the best fit of the experimental RTD data.

Effect of Bypass-Flow on Leaching of Salts in a Cracking Soil in the Nile Delta

Salinity is a major threat to the sustainability of irrigated agriculture in arid and semi-arid regions. Leaching is the primary measure for removing excess salts from the root zone, but not all water applied to the soil surface contributes to the removal of salts. In clayey soils, bypass flow along cracks can occur without being mixed with saline pore water in the matrix. To present a field dataset to quantitatively evaluate the contribution of bypass flow to the leaching of salts, soil sampling and monitoring of groundwater and discharge from a tile drain were carried out in farmland having a cracking soil in the Nile Delta. The electrical conductivities of 1:2 extracts were measured to evaluate the salinity of the soil. The first evidence for the occurrence of significant bypass flow through cracks was the salinity of the pore water, which was nearly triple that of the shallow groundwater and outflow from drainage. Second, the difference in root zone salinity before and after paddy rice cultivation was not significant. Third, the gradient of the groundwater table was very small. in spite of the low saturated hydraulic conductivity. Fourth, the salinity of the outflow from the tile drain dropped just after irrigation or rain. These results indicated that bypass flow through cracks played a significant role in the drainage process in the soil, and that nearly half of the water bypasses through cracks in the field with a cracking soil.

Reconstruction of the 3D pressure field and energy dissipation of a Taylor droplet from a $$\upmu$$PIV measurement

In this study, we reconstruct the 3D pressure field and derive the 3D contributions of the energy dissipation from a 3D3C velocity field measurement of Taylor droplets moving in a horizontal microchannel ($$\rm Ca_c=0.0050$$ Ca c = 0.0050 , $$\rm Re_c=0.0519$$ Re c = 0.0519 , $$\rm Bo=0.0043$$ Bo = 0.0043 , $$\lambda =\tfrac{\eta _{d}}{\eta _{c}}=2.625$$ λ = η d η c = 2.625 ). We divide the pressure field in a wall-proximate part and a core-flow to describe the phenomenology. At the wall, the pressure decreases expectedly in downstream direction. In contrast, we find a reversed pressure gradient in the core of the flow that drives the bypass flow of continuous phase through the corners (gutters) and causes the Taylor droplet’s relative velocity between the faster droplet flow and the slower mean flow. Based on the pressure field, we quantify the driving pressure gradient of the bypass flow and verify a simple estimation method: the geometry of the gutter entrances delivers a Laplace pressure difference. As a direct measure for the viscous dissipation, we calculate the 3D distribution of work done on the flow elements, that is necessary to maintain the stationarity of the Taylor flow. The spatial integration of this distribution provides the overall dissipated energy and allows to identify and quantify different contributions from the individual fluid phases, from the wall-proximate layer and from the flow redirection due to presence of the droplet interface. For the first time, we provide deep insight into the 3D pressure field and the distribution of the energy dissipation in the Taylor flow based on experimentally acquired 3D3C velocity data. We provide the 3D pressure field of and the 3D distribution of work as supplementary material to enable a benchmark for CFD and numerical simulations. Graphical abstract

Re-Examining Factors That Affect Delta Smelt (Hypomesus transpacificus) Entrainment at the State Water Project and Central Valley Project in the Sacramento–San Joaquin Delta

Managing endangered species is challenging when increased rarity leads to an inability to detect their responses to environmental conditions. In the San Francisco Estuary, the state and federally listed Delta Smelt (Hypomesus transpacificus) has declined to record low numbers, elevating concern over entrainment at the State Water Project (SWP) and Central Valley Project (CVP) water export facilities. The objective of this study was to: (1) revisit previous work on factors that affect adult Delta Smelt collected at the SWP and CVP fish collection facilities using updated conceptual models and a new statistical approach; and (2) to determine factors that affect salvage at time-scales of interest to management. Boosted Regression Tree (BRT) models were applied to salvage data at the SWP and CVP, aggregated into two response categories: a “first flush” response that represented daily salvage from the start of the entrainment window to the 50% midpoint of observed salvage, and a “seasonal” response that included daily salvage from the entire entrainment window. Precipitation, sub-adult abundance, Yolo Bypass flow, and exports best explained first flush salvage at both the SWP and CVP. The seasonal models included a similar set of influential variables, but the relative influence of precipitation was lower compared to the first flush models., Yolo Bypass flow was more influential for seasonal salvage at the SWP, compared to the CVP; Old and Middle River flow was more influential for seasonal salvage at the CVP. Although the rank of variable importance that explains salvage differed slightly between first flush and seasonal time-scales, this study suggests that salvage is most influenced by hydrodynamics, water quality, and population abundance. The application of BRT models to predict salvage is limited, because salvage has been low since federal protections were implemented in 2008. Forecast models that integrate real-time variables with fish behavior models may improve Delta Smelt management.