The nozzle spacing is a quite important factor in the design of wastewater discharge projects, which will form multiple jets. In this study, a threedimensional large eddy simulation (LES) model has been developed to investigate the effect of nozzle spacing on the characteristic behaviors of dual jets in wavy cross-flow. The jet's instantaneous velocity is simulated with the synthetic eddy method (SEM). The modeling results shows that the nozzle spacing has a significant effect on the patterns of overlapping effluent clouds, the shielding effect of the front jet and the interaction between dual jets.
Coastal discharge has been frequently used by the wastewater treatment in recent years, which may cause adverse environmental and ecological impacts on the coastal zone. It is of great importance to understand and predict the wastewater movement, with the use of multiple jets, under complex coastal dynamic conditions.
The characteristic of multiple jets in cross-flow (JICF) has been studied both experimentally (i.e., New, T.H. et al., 2015; Ali, 2003; Yu, 2006) and numerically (i.e., Xiao, 2011; Li et al., 2007). New (2015) conducted experiments to investigate dual jets’ trajectories for three nozzle spacing. It was found that the front and rear jets will eventually merge after they exhaust into the cross-flow, and the merged trajectories were found to penetrate deeper into the cross-flow than that of a single JICF. Ali and Yu (2006) experimentally studied interaction of 2-8 tandem jets with different spacing, and found that the effective velocity between consecutive adjacent jets was 0.3~0.7 times the cross-flow attributed to the shielding effect of the leading jet. Gutmark (2011) concluded four distinct vortex structures of a single JICF: horseshoe vortices, jet shear layer vortices, wake vortices, and counter-rotating vortex pair (CVP). Lee (2007) had used the realizable k-ε turbulence model and the SIMPLEC algorithm to investigate the vortices of multiple turbulent jets in cross-flow. It was found that both horseshoe vortices and wake vortices affect the development of the CVP.
Beach erosion is a ubiquitous natural phenomenon worldwide. Submerged berms are widely used in beach nourishment project due to their eco-friendly nature and easy access of material. A series of flume tests were carried out under the guidance of Lightweight Model theory to study the evolution of a submerged berm under the effects of waves. Physical parameters were set up based on a low-energy beach nourishment project with submerged berms. The results indicate that the cross-shore profiles of submerged berms have a significant effect causing asymmetrical shape changes, which is confirmed in field data as well. The crest elevation changes and the duration of profile stabilization are also discussed.
Beach erosion is a ubiquitous natural phenomenon worldwide. According to Xia (2009), most of the sandy beaches in China are experiencing severe erosion processes, retreating at a rate of averaging 1.0~2.0 m each year. Among the various approaches to protect and broaden eroded beaches, beach nourishment is one of the most effective and eco-friendly methods (Dean, 2005). Submerged berms are becoming an increasing used method for beach nourishment due to its eco-friendly nature and easy access of material.
A submerged berm, also known as shoreface nourishment or submerged mound, is defined as dredged material placement in the nearshore area acting as an underwater sandbar (Dean and Dalrymple, 2002). The performance of a submerged berm can include damping of waves in order to shelter of the landward beach and reduce offshore migration, nourishing of the beach directly by means of increasing onshore migration, or a combination of both (Grasso et al., 2011). The evolution of a natural sandbar is a classic issue of coastal engineering on which many studies have been conducted. However, research studies on the evolution of submerged berms are relatively fewer and are typically carried out by means of case studies based on field surveys, especially on low energy sandy beaches.
The discharge of wastewater into coastal waters will form a buoyant jet. The movement will be subjected the coastal dynamics. In this study, the behaviours of a buoyant jet in wavy crossflow are investigated by using the particle image velocimetry (PIV) and planar laser-induced fluorescence (PLIF) techniques. Several large-scale “effluent clouds” existing on the upper part of the buoyant jet, which results from the accelerating or decelerating effect of wave on the crossflow. The wave height, wave period and the buoyancy have significant effect on the dilution of the buoyant jet in wavy crossflow environment.
There is an urgent global requirement for the ocean disposal of urban treated wastewater via submarine outfalls. The fast and effective dilution of the wastewater is expected to reduce its adverse influence on local human and wildlife communities. Hence, it is quite necessary to understand the movement and dilution of wastewater in the coastal waters. The discharged wastewater will form a buoyant jet, subjected by the surrounding coastal dynamics (i.e., wave and/or current).
Over the past decades, the effects of waves or currents on the movement and dilution of a buoyant or non-buoyant jet have been extensively investigated. According the studies of Chin (1988), Chyan and Hwung (1993), Mossa (2004), and Hsiao et al. (2011), the entrainment rate of jets in wave environment is significantly increased by the wave oscillatory motion, resulting in the jets having faster decay of centerline velocity, wider spreading width, larger dilution rate and stronger turbulence than those in stagnant ambience. Chen et al. (2012) and Lin et al. (2013) studied the effect of buoyancy on the movement and dilution of jet in irregular or regular waves. Both results shows that the buoyancy is a quite important parameter dominating the jet behaviours. It was found that the wave effect on the jet entrainment and mixing is considerably weakened under the existence of buoyancy force, resulting in a slower decay rate of centerline velocity and a narrower jet width for the jet with initial buoyancy. Under the effect of current, the jet will be bent-over along the current, with the forming of several large scale vortex structures, including the shear layer vortices, the horseshoe vortices, the wake vortices and the counter-rotating vortex pair (CVP) (Yuan et al., 1999; Hasselbrink and Mungal, 2001; Gopalan et al., 2004; Muppidi and Mahesh, 2005). The dilution of jet in current environment was also investigated by many researchers (e.g. Lee et al., 1987; Huang et al., 1995). And several semi-empirical equations were derived to describe the minimum dilution and the jet trajectory based on the available in-situ and experimental data.
In this study, vorticity analysis is carried out on the ECMWF reanalysis data of sea surface wind speed, to identify the track of tropical cyclones (TCs) in the Northwest Pacific Ocean region over a period of three years (2013-2015). The maximum wind speed in the adjacent of the identified TC centre is also extracted from the ECMWF reanalysis data. The typhoon tracks and the maximum wind speed extracted from reanalysis data are then compared with the Best-Track data to assess the representation of TCs in the ECMWF reanalysis data. The results show that the locations of TC tracks can be reasonably determined from the ECMWF data by the vorticity in the studied period. However, the correlation between the vorticity and intensity of the TC is poor. The maximum wind speed of the TCs are found to be significantly lower than the Best-Track data. This study provides some quantification and guidance on the use of ECMWF reanalysis data for the predictions of storm waves and surges in the NWP region.
In recent years, ERA-Interim, the latest global atmospheric reanalysis dataset developed by ECMWF (the European Centre for Medium- Range Forecasts), have been widely used to provide surface forcing to studies in climate changes and oceanography and coastal engineering. For example, Lv et al. (2014) used the ECMWF ERA-Interim wind data to drive the SWAN wave model and simulate the waves in Bohai Sea. Li et al. (2016) used the same dataset to drive the WAMC4 wave model and simulated the long-term waves in East China Seas. The dataset has been continuously refined to higher resolutions.
The Northwest Pacific Ocean (NWP) region, which includes the East China Seas, the South China Sea and the Japan Sea, has seen the largest occurrence of tropical cyclones (TCs) each year in the world (Landsea, 2000). Tropical cyclone, also called typhoon, is a rapidly rotating storm system characterized by a low-pressure centre, a closed low-level atmospheric circulation and strong winds. The intensity of TCs varies, but in severe cases, TCs can cause devastating damages, particularly in the coastal areas, due to the strong winds, energetic waves and high surge levels. Since the occurrence of TCs is usually confined in a relatively smaller area and particular time, they may be underrepresented in the global scale atmospheric datasets with relatively low resolution, such as the ECWMF reanalysis data. In the past decades, many studies have been carried out to assess this effect. Hart et al. (2007) used 40-year ECMWF ERA-40 to quantify the environmental ‘memory’ of the TC passage. Sriver and Huber (2006) also used the ERA-40 data to calculate the power dissipation of TCs (Emanuel, 2005). Onogi et al. (2007) examined detection frequencies of TCs globally for the ERA-40 and the Japan Meteorological Agency (JMA) 25-year Re-Analysis (JRA-25). It was found that over 80% of TCs were trackable within the JRA-25, but within the ERA-40, the trackable TCs were below 60%.
Coastal discharge of wastewater, which is usually in the form of multiple jets, could be significantly affected by the wave action. In this study, the characteristic behaviours of multiple jets vertically discharged into regular wave environments are investigated by use of the particle image velocimetry (PIV) technique as well as a large eddy simulation (LES) model. The flow field of multiple jets is divided as the separated region, the mixing region and the mixed region. Both the experimental results and the numerical results show that the wave enhances the mixing between adjacent jets and increases the jet spread width.
Coastal discharge has been a frequently used wastewater treatment in recent years, which may cause adverse environmental and ecological impacts on the coastal zone. It is of great importance to understand and predict the behaviors of wastewater movement, which is usually in the form of multiple jets, under complex coastal dynamic conditions, to accurately assess the adverse impacts on the surrounding environment. From the viewpoint of environmental hydraulics, the jet movement can be identified as a near-field process and a far-field process according to different time and distance scales (Roberts, 1999). In the near field, the discharged jet is not only driven by its initial momentum, but also affected by various coastal dynamics such as waves. It will further alter the movement and dilution of wastewater in the far field.
Over the past decades, the effects of regular waves on the jet movement have been extensively investigated both experimentally and numerically. Chin (1987) experimentally found that the surface dilution of the jet in a typical persistent wave environment, was significantly higher than that of the jet in the stagnant ambience. Chin (1988) also developed a Lagrangian integral model and simulated the effect of surface waves on the mixing of submerged jet. Chyan and Hwung (1993) measured the flow field of a vertical round jet discharged into a wave environment and divided the jet-wave interaction into the deflected region, the transition region and the developed region. Mori and Chang (2003), Ryu, Chang and Mori (2005), Chang, Ryu and Mori (2009), Hsiao, Hsu, Lin and Chang (2011) conducted a series of experiments to investigate the behaviours of the horizontal jet discharged into a wave environment. It was found that the wave-to-jet momentum ratio is the most important parameter to characterize the effect of waves to the diffusion of jet. With the increasing of the wave-to-jet momentum ratio, the jet flow pattern was summarized as the symmetric motion, the asymmetric motion and the discontinuous motion. Under the effect of regular waves, the entrainment rate of jets is significantly increased by the wave oscillatory motion, resulting in the jets having faster decay of centerline velocity, wider spreading width, larger dilution rate and stronger turbulence than those in stagnant ambience. The mean velocity and concentration profiles exhibit the “non-Gaussian distribution” or “twin peaks” under the strong wave action (Chyan and Hwung, 1993; Mossa, 2004; Xu, Chen, Zhang, Li, Wang and Hu, 2014).
To study the characteristics of non-equilibrium flocculation process of cohesive sediment, a semi-empirical flocculation model is incorporated into a two-phase model. The model is validated using two data sets of the experiments conducted in a vertical settling column under grid generated turbulent shear conditions. The agreement between the measured data and model results demonstrates the validity of the developed model. It is also found that under the condition of spatially variable shear rate, the suspended sediment concentration strongly influences the floc size.
Flocculation is a special process that distinguish the behavior of cohesive sediment and that of non-cohesive sediment (Klimpel and Hogg, 1986). Slowly sinking matters such as organic matter, primary sediment particle and contaminates are caused to collide and get aggregation to form large rapidly sinking flocs (Burban et al., 1989; Lick et al., 1992). Consequently, the dynamical and physical properties of flocs are different from those of single particles, organic matter and contaminates. This process, namely flocculation, strongly influences the settling velocity of sediment in aquatic environment and complicates the cohesive sediment transport processes (Cuthbertson et al., 2010; Winterwerp, 1998).
It is well known that at least three mechanisms are operative during the flocculation process (aggregation and break up): Brownian motion, Differential settling, and Turbulent motion (Lee et al., 2011; Winterwerp, 1998). It has been concluded that the disaggregation of mud flocs is dominated by Brown motions, and the effects of differential settling and fluid shear can be negligible for small particles (Burban et al., 1989; Lick et al., 1992; McCave, 1984; van Leussen, 1999). The differential settling mechanism is important in still water environment such as water treatment installations (Lick et al., 1993). The scholars have mostly focused the effect of turbulent motions (McCave, 1984; Son and Hsu, 2008; Son and Hsu, 2009; Spicer and Pratsinis, 1996; Winterwerp et al., 2006). This effect was treated as one of the key factors controlling the flocculation process and was introduced into many flocculation models.
Elebiju, Bunmi (BP America) | Ariston, Pierre-Olivier (BP America) | van Gestel, Jean-Paul (BP America) | Murphy, Rachel (BP America) | Chakraborty, Samarjit (BP America) | Jansen, Kjetil (BP America) | Rodenberger, Douglas (Shell America) | White, Roy C. (Shell America) | Chen, Yongping (CGG) | Hren, David (CGG) | Hu, Lingli (CGG) | Huang, Yan (CGG)
Using the Kepler and Ariel Fields as a case study, this paper discusses the processing challenges and solutions applied to a 4D co-processing of Wide Azimuth Towed Streamer (WATS) on Narrow Azimuth Towed Streamer (NATS) data. Unlike a dedicated 4D acquisition, WATS on NATS 4D has relatively low repeatability in terms of acquisition geometry and bandwidth differences. All these factors can negatively impact the extraction of a meaningful 4D signal. In this paper, we demonstrate how processing techniques can help to increase repeatability and enhance 4D signal. We focus on the following 4D processing procedures: 4D co-binning, data matching, and post-migration co-denoise. Due largely to these techniques, the final co-processed volumes show an optimized 4D seismic signal with a median Normalized Root Mean Square (NRMS, which measures the repeatability between base and monitor. Details refer to Kragh and Christie, 2002) of 0.10 along the water bottom and 0.28 above the reservoir.
This paper presents an efficient method to fast generate the ensemble typhoon wind field by using the forecast wind data obtained from several operational weather forecast centers. The weighted bias-removed ensemble mean (WEM) method is utilized to generate the characteristic parameters, i.e., typhoon track and maximum wind speed, for the control typhoon. Based on the error analysis of typhoon forecasts during the training period, 15 ensemble typhoon members are then generated by combination of 5 different typhoon tracks and 3 different maximum wind speeds from those of the control typhoon. Finally 15 ensemble wind fields are generated by applying the Jelesnianski typhoon model on each ensemble member. The generated ensemble wind fields are used in the forecast of storm surge for Typhoon Haikui (1211) and the results show that the ensemble forecast method can effectively increase the reliability and accuracy of the storm surge forecast.
The storm surge during the events of Typhoon Muifa and Typhoon Damrey are numerically modeled and the accuracy is examined by the field observed water level data. The results show that: (1) with the consideration of tidal effect, the accuracy of storm surge modeling results can be notably improved, particularly in the shallow water area; (2) a large-scale anticlockwise circulation flow is formed at the left side of typhoon-affected area, and the maximum typhoon-induced current has a magnitude of 1m/s.
Wastewater discharge into coastal areas, which is usually in the form of turbulent jets, may cause serious environmental problems in the coastal zone. In the near field, the discharged jet is not only driven by its initial momentum, but is also affected by the surrounding coastal dynamic forces, such as tidal currents and waves. In this study, a generic large eddy simulation (LES) model is developed to simulate the jet near-field behaviours in various coastal environments, including cross-flow currents, waves, coexisting waves and cross-flow currents. It is shown that all the modelling results are consistent well with the experimental data, indicating the model is a useful tool to predict the jet initial movements in various coastal environments.