The effects of drainage basin geomorphometry on minimum low flow discharge: the study of small watershed in Kelang River Valley in Peninsular Malaysia

This study investigate the relationships between geomorphometric properties and the minimum low flow discharge of undisturbed drainage basins in the Taman Bukit Cahaya Seri Alam Forest Reserve, Peninsular Malaysia. The drainage basins selected were third-order basins so as to facilitate a common base for sampling and performing an unbiased statistical analyses. Three levels of relationships were observed in the study. Significant relationships existed between the geomorphometric properties as shown by the correlation network analysis; secondly, individual geomorphometric properties were observed to influence minimum flow discharge; and finally, the multiple regression model set up showed that minimum flow discharge(Q min) was dependent of basin area(AU), stream length(LS), maximum relief(Hmax), average relief(HAV) and stream frequency(SF). These findings further enforced other studies of this nature that drainage basins were dynamic and functional entities whose operations were governed by complex interrelationships occurring within the basins. Changes to any of the geomorphometric properties would influence their role as basin regulators thus influencing a change in basin response. In the case of the basin's minimum low flow, a change in any of the properties considered in the regression model influenced the “time to peak' of flow. A shorter time period would mean higher discharge, which is generally considered the prerequisite to flooding. This research also conclude that the role of geomorphometric properties to control the water supply within the stream through out the year even though during the drought and less precipitations months. Drainage basins are sensitive entities and any deteriorations involve will generate reciprocals and response to the water supply as well as the habitat within the areas.

Seasonal and interannual variations of flow discharge from Pearl River into sea

Flow discharge from the river basin into the sea has severe impacts on the immediate vicinity of river channels, estuaries, and coastal areas. This paper analyzes the features and temporal trends of flow discharge at Pearl River＇s three main gauge stations： the Wuzhou, Shijiao, and Boluo gauge stations on the West River, North River, and East River, respectively. The results show no significant trend in annual mean discharge into the sea at the three gauge stations. Changes of monthly mean discharge at the Boluo Gauge Station are evident, and a majority of monthly discharge in the dry season displays significant increasing trends. Furthermore, changes of the extreme discharge are quite evident, with a significant decreasing trend in the annual maximum discharge and a significant increasing trend in the minimum one. The significantly decreasing ratio of the flood discharge to annual discharge at the Boluo Gauge Station indicates that the flow discharge from the East River has increased in the dry season and decreased in the flood season since the construction of dams and reservoirs. At the other two gauge stations, the Wuzhou and Shijiao gauge stations, the seasonal discharge generally does not change perceptibly. Human impacts, especially those pertaining to reservoir and dam construction, appear to be responsible for the seasonal variation of flow discharge. The results indicate that the construction and operation of dams and reservoirs in the East River have a greater influence on flow discharge, which can well explain why the seasonal variation of flow discharge from the East River is more evident.

Discharge evolution law of debris flow based on a sharp bend physical modeling test

For the basins with debris flow development,its channel terrain exhibits a tortuous shape,which significantly restricts the movement of debris flows and leads to severe erosion effects on the concave bank.Therefore,this study aims to analyze the shear force of debris flows within the bend channel.We established the relationship between the shear force and bend curvature through laboratory experiments.Under the long-term erosion by debris flows,the curvature radius of bends gradually increases,however,when this increasing trend reaches an equilibrium state with the intensity of debris flow discharge,there will be no significant change in curvature radius.In general,the activity pattern and discharges of debris flows would remain relatively stable.Hence,we can infer the magnitude of debris flow discharges from the terrain parameters of the bend channel.

Flow fields and packing states in the discharge flow of noncircular particles-A SIPHPM simulation

Although the discharge flow of spherical materials has been extensively explored, the effect of particle shape on discharge is still poorly understood. The present work explores the two-dimensional discharge flow fields of noncircular particles using the soft-sphere-imbedded pseudo-hard particle model method. Rectangular particles having different aspect ratios （Ra = 1, 1.5, 2-5） and regular polygonal particles hav- ing different numbers of sides （Ns = 3-8, 10） are discharged through hopper beds having different orifice widths （Di = 40, 70.77, 99.13, 125.74, 151.13 mm）. The discharge rates of differently shaped particles in different beds are consistent with Beverloo＇s relation. Moreover, the flow fields are computed and eval- uated to study the effects of Ra, Ns, and Di on particle discharge. The characteristics of particle-particle connections in the discharge process are evaluated according to the temporal evolution and spatial dis- tribution of the contact points. Additionally, the effect of the initial packing on the discharge profile is investigated. The findings help clarify the discharge of noncircular particles.

NUMERICAL ANALYSIS OF SIDE DISCHARGES INTO A CHANNEL FLOW USING AN RNG k^(-ε)MODEL

Side discharge into a channel flow is numerically simulated using an RNG based k ε turbulence model. It is shown that the results of the recirculation zone obtained using the RNG k ε model generally agree better with the experimental results compared with those by the standard k ε model. The reason for the improvement of the results obtained using the RNG k ε model over those by the standard k ε model on this flow is analyzed. The flow at small discharge ratios is thoroughly investigated and it is found that the velocity profile at the jet exit is extremely non uniform at small discharge ratios. It is also found that the degree of the non uniformity decreases as the discharge ratio increases, and is very slight for discharge ratios larger than 2.0. The effects of calculation domain, mesh size, wall functions, bed roughness and discharge ratios on the size of separation zone are also investigated in detail.

Estimation of sediment load and erosion of different geological units: A case study from a basin of north-eastern Iran

Erosion of geological units and sediment load in rivers can be considered as the serious problems in recent decades.Increasing sediment loads generate major hazards for water resources development,particularly in terms of loss of reservoir storage due to sedimentation and siltation of water distribution systems.In this paper,the performance of four sediment rating curve (SRC) development methods was evaluated for the Shirin Darreh River(SDR) basin (1750 km^(2)),located in North Khorasan Province,Iran.Data of flow discharge (Q) and suspended sediment flux (SSF)(Q-SSF pairs,N=957)and daily flow discharge,recorded by the Regional Water Company of North Khorasan (RWCNK) at the Qaleh-Barbar (QB) gauging site during 1989-2018 were used.The flow discharge classification method performed best by meeting the desired criteria of most statistical indices,including normalized root mean square error (NRMSE),mean bias error (MBE),mean absolute error (MAE),index of agreement (d),and coefficient of determination (R^(2)).Based on the optimized method,the rate of suspended sediment transportation at the study site was estimated about2.7×10^(6) ton year^(-1).Erodibility of the exposed formations in the study area was estimated based on a factorial scoring model (FSM).Three indices,focused on the outcrop and erodibility,were calculated for the geological units at sub-basin and total scales.Marl deposits are the most extensive geological unit in the three sub-basins and the maximum formation outcrop ratio (FOR) and participation in erosion (PCE)were obtained for these rocks at total scale.In fact,marl unit can be regarded as the main source to supply the suspended sediments in the study basin.

Rate constants for the reaction of hydroxyl radicals with HFC-134a

Rate constants for the reaction of hydroxyl radicals with HFC 134a (CH 2FCF 3) have been measured by the discharge flow resonance fluorescence (DF RF) technique over the temperature range 288—370 K. The derived Arrhenius equation is: k″ =(1.27±0.16)×10 -12 exp(-(1662±41)/ T )cm 3/(mol·s). The tropospheric lifetime of HFC 134a is estimated to be 10.5 years, which is in excellent agreement with the most recent results.

Applying chemical engineering concepts to non-thermal plasma reactors

Process scale-up remains a considerable challenge for environmental applications of non-thermal plasmas.Undersanding the impact of reactor hydrodynamics in the performance of the process is a key step to overcome this challenge.In this work,we apply chemical engineering concepts to analyse the impact that different non-thermal plasma reactor configurations and regimes,such as laminar or plug flow,may have on the reactor performance.We do this in the particular context of the removal of pollutants by non-thermal plasmas,for which a simplified model is available.We generalise this model to different reactor configurations and,under certain hypotheses,we show that a reactor in the laminar regime may have a behaviour significantly different from one in the plug flow regime,often assumed in the non-thermal plasma literature.On the other hand,we show that a packed-bed reactor behaves very similarly to one in the plug flow regime.Beyond those results,the reader will find in this work a quick introduction to chemical reaction engineering concepts.

Experimental and Numerical Investigation of Impingement Heat Transfer on Target Plate with Streamlined Roughness Element at Maximum Crossflow Condition

A combined experimental and numerical investigation of the heat transfer and flow characteristics of the roughened target plate has been conducted.All the data are compared with the flat plate.Three novel streamlined roughness elements are proposed:similar round protuberance,similar trapezoidal straight rib,and similar trapezoidal curved rib.The experiments are carried out in a perspex model using the transient thermochromic liquid crystal method.The effect of jet Reynolds number,rib height,and rib shape on the Nusselt number and flow discharge coefficient has been investigated.Higher ribs provide higher heat transfer enhancement.The curved ribs provide better heat transfer performance.Within the experimental scope,combined straight rib plate and combined curved rib plate increase the area averaged Nusselt number by 11.5%and 13.8%respectively.The experiment is complemented by a numerical part,which can provide flow field analysis and the Nusselt number on the surface of the small size roughness element.The numerical results show the protuberance can shorten the nozzle to plate distance and make the shifting point move forward.The ribs have a guidance effect on crossflow and reduce the transverse interference to the downstream jet.The transferred heat flux caused by the side surface of the roughness element is very obvious.The heat flux contributed by the side surface of the protuberance and ribs can reach 26%and 10%respectively.

Hydraulics of crest spillway with large unit discharge and low Froude number

With respect to the crest spillway with large unit discharge and low Froude number, the hydraulics of the slit-type energy dissipater at the outlet should be noticed due to the complicated flow regimes. In the present paper, some issues about hydraulic characteristics were experimentally investigated by means of five slit-type outlets and four tetrahedrons, including the flow choking, impact to river banks and jet trajectory. The main findings are as follows. The critical Froude number for the flow choking decreases with increasing outlet width of the slit-type energy dissipater. If the flow Froude number is expressed by the parameters just before this energy dissipater, the tetrahedron placed inside the side wall of the outlet could efficiently avoid the flow impact to the river bank of same side, and compared with the jet trajectory of the slit-type energy dissipater, the outlet with tetrahedron has different trajectory trend, i.e., the distance of the jet trajectory decreases with the increase of the water head due to special form of the outlet tetrahedron.

Effects of volumetric fraction and included angle of composite particles on the discharge of binary mixtures in hoppers

The discharge behavior of particles is important in many industrial applications,such as in the core of a pebble bed reactor,which uses a hopper bed filled with many large particles.In this work,a mixture composed of two particle types,freely discharged from a pebble bed,is simulated using the discreteelement method.One is a spherical pebble of diameter equal to that of the fuel pebble of the reactor.The other is a composite particle comprising three spherical pebbles bonded together.The included angleαof the three pebbles characterized the particle conformation,which may affect the discharge behavior of the mixture.The effects of volume fraction of the multi-sphere x(equivalent to the number fraction)on the discharge are also analyzed.Flow patterns,number flow rate,discharge velocity,and mean force of the mixture are computed to help in revealing discharge features.The results show that increasing eitherαor x reduces the discharge flow rate.Fittings and correlations give a quantitative evaluation of the independent effects ofαand x.The analysis of velocity and force explains the mechanism relevant to the main influencing factorsαand x.The results are helpful in gaining a better understanding of the discharge feature of binary mixtures and in providing a quantitative evaluation of the discharge behavior of the reactor core,especially adverse failure conditions.

Turbulent boundary layer separation control using plasma actuator at Reynolds number 2000000

An experimental investigation was conducted to evaluate the effect of symmetrical plasma actuators on turbulent boundary layer separation control at high Reynolds number. Compared with the traditional control method of plasma actuator, the whole test model was made of aluminum and acted as a covered electrode of the symmetrical plasma actuator. The experimental study of plasma actuators＇ effect on surrounding air, a canonical zero-pressure gradient turbulent boundary, was carried out using particle image velocimetry （PIV） and laser Doppler velocimetry （LDV） in the 0.75 m × 0.75 m low speed wind tunnel to reveal the symmetrical plasma actuator characterization in an external flow. A half model of wing-body configuration was experimentally investigated in the 3.2 m low speed wind tunnel with a six-component strain gauge balance and PIV. The results show that the turbulent boundary layer separation of wing can be obviously suppressed and the maximum lift coefficient is improved at high Reynolds number with the symmetrical plasma actuator. It turns out that the maximum lift coefficient increased by approximately 8.98% and the stall angle of attack was delayed by approximately 2° at Reynolds number 2 ×10……6. The effective mechanism for the turbulent separation control by the symmetrical plasma actuators is to induce the vortex near the wing surface which could create the relatively large- scale disturbance and promote momentum mixing between low speed flow and main flow regions.