Hydrodynamic Vortex Separator Research Articles

Optimization of hydrodynamic vortex separator for removal of sand particles from storm water by computational fluid dynamics

Optimization of hydrodynamic vortex separator for removal of sand particles from storm water by computational fluid dynamics

Numerical study of dense solid-liquid flow in hydrodynamic vortex separator applied in recirculating biofloc technology system

Hydrocyclone separation technique has commonly been applied in engineering for solid-liquid separation. In aquaculture, since Hydrodynamic Vortex Separator (HDVS) is able to control flocs concentration effectively, the Recirculating Biofloc Technology (RBFT) has been gradually acknowledged (Zhu et al., 2016). In order to operate RBFT system at maximum performance, the removal efficiency of HDVS at different Hydraulic Retention Time (HRT) must be fully predictable. The aim of this work is to investigate the relationship between separation efficiency and HRT of HDVS applied in RBFT system, through Computational Fluid Dynamics (CFD) method. For this, a three-dimensional unsteady transient model was developed to simulate the hydrodynamics in HDVS based on the commercial software Workbenching 17.0. A Two Fluid Model (TFM) using kinetic theory of granular flow (KTGF) has been developed to describe the dense solid-liquid (flocs-water) flow field of HDVS in RBFT system. Additionally, the Reynolds averaged Navier-Stokes (RANS) equations with Reynolds stress turbulence model (RSM) are solved by use of the finite volume method based on the SIMPLE pressure correction algorithm in the computational domain. Finally, pilot-scale studies were conducted to evaluate the accuracy and precision of simulation models applied. The results indicate that the flocs removal efficiency of HDVS obtained from tests were less than that from the simulation results at three different HRTs. But it decreased with the decline of HRT both for experiment and simulation. Additionally, the CFD model proposed can enhance the fundamental understanding of the effects of HRT on separation efficiency and at the same time, probably coupled with physical experiment whenever necessary, offer a more reliable way for optimum control of HDVS under varying conditions. Based on the simulation results, the flocs management in RBFT system is briefly discussed.

Performance evaluation of Hydrodynamic Vortex Separator at different hydraulic retention times applied in Recirculating Biofloc Technology system

Abstract. Recirculating biofloc technology (RBFT) has been gradually acknowledged for its positive effect on the control of biofloc concentration using a hydrodynamic vortex separator (HDVS). To operate an RBFT system at maximum performance, the removal efficiency of an HDVS at different hydraulic retention times (HRTs) must be fully predictable. Hence, a numerical study of the fluid flow and particle dynamics was performed to characterize the performance of an HDVS at varying HRTs. First, flow simulation was conducted to determine an economical mesh size at an HRT of 248 s. Then, with respect to the total suspended solids (TSS) in the RBFT system and the physical properties of the flocs, two-way coupling of the dense discrete phase model (DDPM) and discrete element model (DEM) methods was used to predict floc tracking in an HDVS. Additionally, the Reynolds averaged Navier-Stokes (RANS) equations with the Reynolds stress turbulence model (RSM) were solved using the finite volume method based on the semi-implicit method pressure-linked equations (SIMPLE) pressure correction algorithm in the computational domain. Finally, pilot-scale studies were conducted to verify the simulation models. Based on the simulation results, floc management in an RBFT system is briefly discussed. Due to limited research on the numerical simulation and operating conditions of an HDVS in an RBFT system, this article describes an original investigation of the modeling approach. Keywords: Computational fluid dynamics, Dense discrete phase model, Discrete element model, Floc management, Flow field, Removal efficiency, Total suspend solids.

Removing Grit During Wastewater Treatment: CFD Analysis of HDVS Performance.

Computational Fluid Dynamics (CFD) was used to simulate the grit and sand separation effectiveness of a typical hydrodynamic vortex separator (HDVS) system. The analysis examined the influences on the separator efficiency of: flow rate, fluid viscosities, total suspended solids (TSS), and particle size and distribution. It was found that separator efficiency for a wide range of these independent variables could be consolidated into a few curves based on the particle fall velocity to separator inflow velocity ratio, Ws/Vin. Based on CFD analysis it was also determined that systems of different sizes with length scale ratios ranging from 1 to 10 performed similarly when Ws/Vin and TSS were held constant. The CFD results have also been compared to a limited range of experimental data.

TRACER STUDY INVESTIGATION INTO HYDRODYNAMIC VORTEX SEPARATOR CHARACTERIZATION

This study describes the macromixing within a hydrodynamic vortex separator and considers its potential as a disinfectant contact tank. It is typically used in the sedimentation process during the treatment of sewage. The macromixing was investigated by conducting tracer experiments from which are retention time distribution was obtained and interpreted to characterize the mixing. The separator was operated in a continuous mode with no base flow, and the retention-time distribution was obtained using a pulse input for a range of the flow-rates. The method of moments was used to obtain various functions such as axial dispersion and tanks-in-series model parameters. The study revealed that the HDVS is best treated as an imperfect plug-flow mixing device with a large amount of dispersion.

Removal Characteristic of Road Deposit and Contained Lead in the Road Surface Drainage Using a Hydrodynamic Vortex Separator

Removal Characteristic of Road Deposit and Contained Lead in the Road Surface Drainage Using a Hydrodynamic Vortex Separator

Residence time study of a hydrodynamic vortex separator applied to predicting disinfection performance

The fluid residence time characterization of a 3.4 m diameter hydrodynamic vortex separator (HDVS) has been carried out under laboratory conditions. Computational fluid dynamics (CFD) modelling has then been undertaken for the same conditions at which the experimental data were collected and validated against the experimental results, for which reasonable correspondence has been found. Using the results from the CFD modelling and batch inactivation results from the disinfection of secondary treated wastewater, it is shown that the theoretical performance of an HDVS as a contact vessel for disinfection can be determined and the practical applicability of an HDVS for disinfection is confirmed.

Assessment of residence time in a hydrodynamic vortex separator by applying distribution models

A number of models exist to simulate the residence time distribution (RTD) of a system or process. Four of these models known as the tanks in series model, axial dispersion model (ADM), aggregated dead zone model, and the advection dispersion equation, have been used to assess which is most suitable for representing the RTD of a hydrodynamic vortex separator (HDVS) when compared to RTD measurements taken under laboratory conditions on a full-scale 3.4 m diameter unit. Computational fluid dynamics (CFD) is also used to model the HDVS and compare with the RTD models and experimental measurements. It has been shown that the fit by each of the RTD models to observed RTDs vary quite considerably, with the ADM being the most appropriate for the HDVS studied, based on having the highest R t2 value. Given the number of model variables that influence CFD predictions, the outputs from the CFD models appear to be reasonable.

Experimental study of a hydrodynamic vortex separator

A hydrodynamic vortex separator (HDVS) has been studied under laboratory conditions by using a specifically designed rig. Pressure tapping points placed at eight locations, six external and two internal, have revealed an even radial pressure distribution on the outer walls and central shaft. The ability of the HDVS to separate particulates has been studied. The particulates have been characterized by measurements of particle diameter and settling velocity, which have allowed efficiency cusps to be plotted against dimensionless groups used by other researchers. Owing to an unsatisfactory reduction of the data to a single curve by plotting the efficiency against dimensionless groups, an efficiency law has been determined based on the logistic equation and describes the separation efficiency in terms of the inlet flowrate, volume of the separator, and particle diameter and density.

Computational fluid dynamic prediction of the residence time of a vortex separator applied to disinfection

A Hydrodynamic Vortex Separator (HDVS) has been modelled using Computational Fluid Dynamics (CFD) in order to predict the residence time of the fluid at the overflow and underflow outlets. A technique which was developed for use in Heating, Ventilation and Air Conditioning (HVAC) was used to determine the residence time and the results have been compared with those determined experimentally. It is shown that in using CFD, it is possible to predict the mean residence time of the fluid and to study the response to a pulse injection of tracer. It is also shown that it is possible to apply these techniques to predict the mean survival rate of bacteria in a combined separation and disinfection process.

Computational fluid dynamic prediction of the residence time distribution of a prototype hydrodynamic vortex separator operating with a base flow component

A hydrodynamic vortex separator (HDVS) has been modelled using computational fluid dynamics (CFD) in order to accurately determine the residence time of the fluid at the two outlets of the HDVS using a technique that was developed for use in heating, ventilation, and air conditioning (HVAC). The results have been compared with experimental data [1]. It is shown that, in using CFD, it is possible to study the response to a variety of inputs, and also to determine the mean residence time of the fluid within the separator. Although the technique used for determining the residence time was developed for use in HVAC, it is shown here to be applicable for the analysis of hydraulic systems, specifically, wastewater treatment systems.

Residence time distribution of a model hydrodynamic vortex separator

This study investigates the macromixing within a hydrodynamic vortex separator (HDVS). The device is a scale model of a prototype unit and is operated with zero baseflow. The device under investigation is typically used for the removal of settleable and colloidal solids. The macromixing is investigated by conducting tracer experiments from which the residence time distribution (RTD) is obtained and interpreted to characterise the mixing regime within the HDVS. The method of moments and non-linear regression are used to obtain various RTD functions and flow-model parameters to aid in the characterisation of the device's mixing regime and the degree of any non-ideal flow behaviour. The axial dispersion model (ADM) and tanks-in-series model (TISM) are used in this study. The RTD imperfectly approximates a plug-flow distribution but, the device has some amount of dispersion and is equal to approximately 2–3 perfectly stirred tanks in series. The ADM seems to give a closer representation of the experimental curves compared to the TISM. The sludge hopper appears to be acting as a stagnant zone.

Investigation Into the Retention-Time Distribution of a Hydrodynamic Vortex Separator

This study describes the macromixing within a hydro-dynamic vortex separator and considers its potential as a disinfectant contact tank. It is typically used in the sedimentation process during the treatment of sewage. The macromixing was investigated by conducting tracer experiments from which the retention time distribution was obtained and interpreted to characterize the mixing. The separator was operated in a continuous mode with no baseflow, and the retention-time distribution was obtained using a pulse input for a range of flow-rates. The method of moments was used to obtain various functions and axial dispersion and tanks-in-series model parameters.