Effects of hydropeaking on drift, stranding and community composition of macroinvertebrates: a field experimental approach in three regulated Swiss rivers

Hydropeaking operation leads to fluctuations in wetted area between base and peak flow and increases discharge-related hydraulic forces (e.g., flow velocity). These processes promote macroinvertebrate drift and stranding, often affecting benthic abundance and biomass. Our field experimental study – conducted in three hydropeaking-regulated Swiss rivers – aimed to quantify (i) the short-term effects of the combined increase in flow amplitude and up-ramping rate based on macroinvertebrate drift and stranding, as well as (ii) long-term effects based on the established community composition. Hydropeaking led to increased macroinvertebrate drift compared to base flow and to unaffected residual flow reaches. Moreover, stranding of macroinvertebrates was positively related to drift, especially during the up-ramping phase. Flow velocity and up-ramping rate were identified as major determinants for macroinvertebrate drift, while flow ratio and down-ramping rate for stranding. Particularly high sensitivity towards HP was found for Limnephilidae, whereas Heptageniidae seemed to be resistant in respect to short and long-term hydropeaking effects. In the long-term, hydropeaking did not considerably reduce benthic density of most taxa, especially of some highly resistant and resilient taxa such as Chironomidae and Baetidae, which dominated the community composition even though they showed comparably high drift and stranding responses. Therefore, we argue that high passive drift and/or stranding, especially of individual-rich taxa, does not necessarily indicate strong hydropeaking sensitivity. Finally, our results demonstrate the necessity to consider the differences in river-specific morphological complexity and hydropeaking intensity, since these factors strongly influence the community composition and short-term drift and stranding response of macroinvertebrates to hydropower pressure.

Role of E×B drift in double-peak density distribution for the new lower tungsten divertor with unfavorable B t on EAST

Doubly peaked density distribution is expected not only to affect the plasma-wetted area at divertor plates, but also to correlate with the upstream density profile and hence characteristics of MHD activities in tokamak plasmas [H. Q. Wang et al., Phys. Rev. Lett. 124, 195002 (2020)]. Clarifying its origination is important to understand the compatibility between power/particle exhausts in divertor and high-performance core plasmas which is required by present-day and future tokamak devices. In this paper, we analyzed the double-peak density profile appeared in the modeling during the physics design phase of the new lower tungsten divertor for EAST by using comprehensive 2D SOLPS-ITER code package including full drifts and currents, with concentrations on unfavorable magnetic field (ion B×∇B drift is directed away from the primary X-point). The results indicate that E×B drift induced by plasma potential gradient near the target, which is closely related to the divertor state, plays essential roles in the formation of double-peak profile at the target: (1) Large enough radial Ep×B drift produces a broadened high-density region; (2) Strong poloidal Er×B drift drives a significant particle sink and creates a valley on the high-density profile. Thus, the simulation results can explain why this kind of doubly peaked density profile is usually observed at the high-recycling divertor regime. In addition, features of the double-peak ion saturation current distribution measured in preliminary experiments testing the new lower tungsten divertor are qualitatively consistent with the simulations.

A key design parameter proposal for aerodynamically efficient subsonic blended wing body

Purpose Blended wing body (BWB) is a very advantageous design in terms of low fuel consumption, low emission and low noise levels. Because of these advantages, the BWB is a candidate to become the commercial passenger aircraft of the future by providing a paradigm shift in conventional designs. This paper aims to propose a key design parameter for wing sizing of subsonic BWB and a performance parameter for calculating the lift/drag ratio values of BWBs. Design/methodology/approach The parameter proposed in the study is based on the square/cube law, that is, the idea that the wetted area is proportional to the power of 2/3 of the weight. Data on the weight, wing area, wingspan, lift-to-drag (L/D) ratio for 19 BWB used in the analyzes were compiled from the published literature and a theoretical methodology was developed to estimate the maximum lift to drag ratio of BWBs. The accuracy of the proposed key design parameter was questioned by comparing the estimated L/Dmax values with the actual values. Findings In the current study, it is claimed that the wingspan/(take-off gross weight)(1/3) parameter provides an L/D efficiency coefficient regardless of aircraft size. The proposed key design parameter is useful both for small-scale BWB, that is unmanned aerial vehicles BWB and for large-scale BWB designs. Therefore, the b/Wg(1/3) parameter offers a dimensionless L/D efficiency coefficient for BWB designs of different scales. The wetted aspect ratio explains how low aspect ratio (AR)-BWB designs can compete with high AR-tube-and-wing designs. The key parameter is also useful for getting an idea of good or bad BWB with design and performance data published in the literature. As a result, reducing the blending area and designing a smaller central body are typical features of aerodynamically efficient BWB. Originality/value As the role of the square/cube law in the conceptual aircraft design stage has not been sufficiently studied in the literature, the application of this law to BWBs, a new generation of designs, makes the study original. Estimation of the wetted area ratio using only wingspan and gross weight data is an alternative and practical method for assessing the aerodynamic performance of the BWB. According to the model proposed in the current study, reducing the take-off gross weight of the BWBs using lighter building materials and designing with a larger wingspan (b) are the main recommendations for an aerodynamically efficient BWB.

Theoretical model proposal on direct calculation of wetted area and maximum lift-to-drag ratio

Purpose As measuring flight performance by experimental methods requires a lot of effort and cost, theoretical models can bring new perspectives to aircraft design. This paper aims to propose a model on the direct calculation of wetted area and L/Dmax. Design/methodology/approach Model is based on idea that the wetted area is proportional to aircraft gross weight to the power of 2/3 (Wg2/3). Aerodynamic underpinning of this method is based on the square–cube law and the claim that parasitic drag is related to the Swet/Swing. The equation proposed by Raymer was used to find the L/Dmax estimate based on the calculated wetted area. The accuracy of the theoretical approach was measured by comparing the L/Dmax values found in the reference literature and the L/Dmax values predicted by the theoretical approach. Findings Proposed theoretical L/Dmax estimate matches with the actual L/Dmax data in different types of aircraft. Among the conventional tube-wing design, only the sailplanes have a very low Swet/Swing. The Swet/Swing of flying wings, blended wing bodies (BWBs) and large delta wings are lower than conventional tube-wing design. Lower relative wetted area (Swet/Swing) is the key design criterion in high L/Dmax targeted designs. Originality/value The proposed model could be used in wing sizing according to the targeted L/Dmax value in aircraft design. The approach can be used to estimate the effect of varying gross weight on L/Dmax. In addition, the model contributes to the L/Dmax estimation of unusual designs, such as variable-sweep wing, large delta wings, flying wings and BWBs. This study is valuable in that it reveals that L/Dmax value can be predicted only with aspect ratio, gross weight (Wg) and wing area (Swing) data.

Influence of Surface Roughness on the Flat-Plate Boundary Layer Transition Under a High-Lift Airfoil Pressure Gradient and Low Freestream Turbulence

Effects of surface roughness on the transition of flat-plate boundary layers under a high-lift airfoil pressure gradient with low incoming freestream turbulence level have been investigated. Time-resolved streamwise and wall-normal velocity fields with surface roughness values of Ra/C = 0.065·10−5, 4.417·10−5 and 7.428·10−5 have been measured at a fixed Reynolds number of 5.2·105 and freestream turbulence intensity of 0.2%. For the reference Smooth surface of Ra/C = 0.065·10−5, a laminar separation bubble forms from about 64% to 83% of the chord length. Displacement thickness increases downstream of separation and then decreases during the transition (reattachment), and momentum thickness increases due to the vortices shed from the separation bubble. Increasing surface roughness has little impact on the laminar boundary layer separation onset but reduces the height and length of the separation bubble and induces earlier transition. For Ra/C = 4.417·10−5, displacement thickness during transition is slightly thinner and the overall momentum deficit is slightly lower than those for Ra/C = 0.065·10−5. For Ra/C = 7.428·10−5, the separation bubble becomes hardly visible as the transition mode approaches the attached mode, and turbulent mixing by the wall-bounded turbulence becomes dominant. In addition, the portion of turbulent wetted area increases due to earlier transition, and momentum deficit increases more rapidly in the turbulent wetted area. Thus, the overall momentum deficit for Ra/C = 7.428·10−5 is larger than that for Ra/C = 0.065·10−5.

An experimental method to study the absorption capacity of paper towels

This study proposes an experimental method for the in-plane liquid wicking to determine the absorption capacity of retail paper towels. Individual plies of the paper towels were tested to minimize the transverse wicking effects on surface wetting. The method involves arbitrary point source injection of liquid into the paper towel surface while recording microscopic images of the wetted areas as liquid spreads. The samples were selected from two main manufacturing processes: conventional wet pressing and through air drying. The tested liquids were water and decane with various driving forces. Two distinct imaging systems, infrared light absorption imaging and visible light transmission imaging, monitored and recorded the wetting process. The wetted regions were calculated to generate the wetting graphs, which illustrate both the dynamic and static wetting behaviors.It was found the amount of driving force has a negligible effect on the maximum wetted area formed on the surface.So, the maximum wetted area and the paper grammage were applied to determine the absorption capacity of the tested towels. Moreover, the absorption capacity results were validated by the basket-immersion test method (ISO 12625-8).Therefore, the proposed method in this work enables quantification of the absorption capacity of papertowels.

A daily water balance model with a dynamic wetted area for estimating drainage from soil moisture observations in an irrigated orchard

<p>Drainage below the root zone of irrigated crops and trees is often an unknown component of the water balance. This drainage water could recharge underlying aquifers and flow to streams and is not part of water consumed by crops, as used in water productivity computations. Drainage from fields with irrigation systems that wet only part of the soil is difficult to estimate. The objective of the research was to develop a water balance model with a dynamic wetted area for analyzing soil water balance components from daily soil moisture observations. The method was applied in an olive orchard in Cyprus, with approximately 35% canopy cover. Soil moisture sensors (SMT100, Truebner and 5TM, Decagon) were installed at six trees, at 10-, 20-, 40- and 60-cm depth, approximately 90 cm from the trunk of the tree. Soil moisture was recorded hourly. The trees were irrigated weekly, with a single spaghetti tube with a discharge rate of approximately 135 L/hr. Daily reference evapotranspiration was computed with the Penman-Monteith equation from meteorological observations recorded inside the orchard (WS500, Lufft). Rainfall was measured with a tipping bucket rain gauge (15189, Lambrecht).</p><p>The model computes a daily volumetric water balance for the canopy area of the tree. During the irrigation season, soil moisture observations were assumed to represent the soil volume wetted by irrigation. Drainage below the 70-cm root zone occurred when soil moisture exceeded the field capacity, as derived from hourly observations. A canopy-area crop coefficient (Kcc-max) was estimated for all irrigation days without drainage by minimizing the sum of the daily evapotranspiration in excess of the maximum evapotranspiration (Kcc-max ETo). This one-sided error was controlled by maintaining a positive difference between Kcc-max and Kcc the day after irrigation. Wetted areas were subsequently computed for all irrigation days without drainage. For irrigation days with soil moisture above field capacity, the wetted area was adjusted manually, such that drainage was smaller on the second day than on the irrigation day, using a Kcc-max for both days. During the May to November 2019 irrigation season, drainage was 8 mm over the field area, for a field capacity of 36%, a Kcc-max of 1.3, and an error of 16 mm. Assuming a field capacity of 38%, drainage was 3 mm over the field area, with a Kcc-max of 1.4, and an error of 17 mm. Overall, the model provided a quick and robust way of estimating the irrigation water balance components.</p><p>This research has received financial support from the ERANETMED3 program, as part of the ISOMED project (Environmental Isotope Techniques for Water Flow Accounting), funded through the Cyprus Research and Innovation Foundation.</p>

Modeling Moisture Redistribution of Pulse Drip Irrigation Systems by Soil and System Parameters: New Regression-based Approaches

One of the strategies for increasing water use efficiency and reducing deep percolation drip irrigation systems is considering the patterns of moisture redistribution after cut-offing the irrigation process. An experimental study was conducted in the present research to evaluate the moisture redistribution process under surface and subsurface pulse drip irrigation systems and developing new regression-based methodologies for estimating moisture redistribution dimensions using both the soil and system parameters together. A physical model was made and the experiments were performed on three different types of soil texture (light, medium, and heavy) with three emitter flow rates (2, 4, and 6 lit/hr) in three emitter installation depths (0, 15, and 30 cm). The experiments were conducted for both continuous (CI) and pulse (PI) irrigation modes. The results showed that significant amounts of wetting dimensions and wetted area of the moisture bulb are related to post-cut-offing stage. Then, using the nonlinear regression analysis, several models were proposed to estimate the horizontal and vertical redistribution pattern as well as the wetted area (upper and lower parts of the emitter). The comparison of the measured and the stimulated values indicated that the non-linear regression models simulated the parameters associated with redistribution, accurately.