Flow Tank Research Articles

A new field correction method for PIV measurements based on mutual information: Case study on a stirred tank flow

Particle image velocimetry (PIV) is an experimental approach widely used to investigate the flow inside stirred tanks. PIV noise sources deteriorate the velocity fields and compromise the measurements, mainly in the estimation of the turbulent parameters. PIV correction approaches based on the primary peak ratio (PPR), namely the ratio between the primary correlation peak to the second highest peak, are used when identifying outliers in the velocity field becomes difficult. However, in some cases, PPR is not sensitive to noise sources and may fail to identify outliers. Therefore, this work proposes a new method of field correction based on mutual information, which is estimated by dividing the height of the cross-correlation peak by the magnitude of the autocorrelation. Analysis were performed using PIV data measured in a 50 L stirred tank. Results show that the proposed methodology can be a valuable tool for the correction of noisy fields.

Experimental Characterization of Admittance Meter With Crude Oil Emulsions

Measuring water content is useful in the oil industry to quantify the actual amount of oil being produced. This extent is used in the processes of control and transfer of custody in tank farms, flow stations, and others. In this study, to determine the water content with an admittance measuring device, a characterization was performed with emulsions to identify the behavior of the sensor against this type of fluid. The device has facing electrodes parallel flat. Emulsions O/W and W/O were prepared in the laboratory with heavy oil at laboratory temperature conditions. The capacitance measurement is used to calculate the value of relative permittivity of the fluid (εm) and conductance is used to calculate the conductivity of the mixture (σm). The results of water content measurements showed the sensor response is related to the continuous phases of the emulsions. In addition, these measurements indicated that a characterization of the electrical behavior of the emulsions, as well as the effect of the formulation of the emulsion, can be made using this equipment.

Haline Convection within a Fresh-Saline Water Interface in a Stratified Coastal Aquifer Induced by Tide

Sea-tide effects on the fresh-saline water interface (FSI) in a stratified coastal aquifer are examined through laboratory experiments. The physical model, a two-dimensional rectangular flow tank, is filled with layered aquifers and aquitards. The aquifers serve as the main entrances/exits of water to/from the system through significant horizontal flows, creating unstable conditions of heavier saline water above lighter freshwater for short periods of time. Several processes create mixing; this instability results in haline convection, creating downward fingering, stable rising of horizontal saltwater front, and unstable upward fingerings of flushing freshwater. The time lag between the sea tide fluctuations and the emergence of adequate fresh- and saltwater is higher in a stratified system compared to a homogeneous system. Furthermore, longer tide cycles lead to the enlargement of the FSI’s toe horizontal movement range. The combination of tidal forcing with a layering aquifer structure leads to a wider FSI by creating a significant salt- and freshwater mixing inside each layer, vertical flows between the layers, and saltwater bodies at isolated areas. Haline convection within the FSI might be the reason for the wider fresh-saline interfaces that are found in field studies.

Kinetic Data for Continuous Processes from Liquid‐Liquid Loop Reactor Experiments

AbstractProcess engineering is based on models, which are preferably established at laboratory scale under near‐service conditions. Here, for the first time, a kinetic study of the basic hydrolysis of ethyl acetate was performed with a small volume liquid‐liquid loop reactor satisfying these criteria. The activation energy and pre‐exponential factor were determined that agreed with data from the literature. Acquired data could be successfully transferred to well‐established ideal reactor models such as continuous stirred tank or plug flow reactors. It was, thus, possible to show that a simply scalable loop reactor, requiring only small amounts of substrate and producing minimum waste, can serve as a tool for kinetic studies of continuous processes.

The influence of oriented external electric field on lipase catalyzed triglyceride hydrolysis

The use of microbial lipases for the hydrolysis of natural oils such as triglyceride esters is a green alternative to conventional processes to produce high value-added chemicals. Biocatalysis using lipases in aqueous solutions is limited often by instabilities, slow kinetics due to mass transfer limitations, and by challenges of economic lipase recycling. Prior work has shown that mass transfer rates and reaction rates can be intensified by increasing interfacial area using electrostatic spray reactors. However, the possible effect of oriented external electrical field on the lipase catalytic activity has hitherto not been considered. In this study, the performance of microbial lipase derived from Candida rugosa in aqueous solutions was analyzed in the presence of a steady DC externally applied electrical voltage. The reaction was conducted in three different batch type reactors, quiescent (fixed interface), stirred tank, and tubular flow system. In each of the three reactor systems it was concluded that the oriented external electrical field has a positive effect on reaction independently of interfacial area. Further studies conducted using reverse polarity, increased electrode distance and for an immobilized lipase system have shown that lipase undergoes conformational changes due to an oriented external electrical field is the main driving mechanism for this enhanced performance.

Effect of the contact tank geometry on disinfection efficiency

Disinfection is a sanitary treatment present in both drinking water and wastewater treatment plants aimed at removing pathogenic microorganisms able to damage the human health. The focus of this study is to apply Computational Fluid Dynamics (CFD) to study and to improve the disinfection efficiency through the optimization of the hydrodynamics inside the disinfection tank. Numerous literature studies have shown that water flow inside traditional multichamber tanks is highly turbulent because of the development of large as well as small vortices in which flow velocity decreases or even vanishes (dead zones). These turbulent phenomena are responsible of an increase of the real residence time, compared to the theoretical one, causing poor disinfection and the development of unwanted by-products. In the present analysis, Large Eddy Simulation (LES) is used to simulate three-dimensional turbulent flow and disinfectant transport in different contact tanks using a structured finite-volume discretization. The results show how the baffles’ geometry, as well as the design of technical and construction details, influences the hydraulic retention time of the disinfectant, varying the disinfection efficiency. In particular, the creation of horizontal baffles inside the vertical baffle chambers reduces the free space and extends the flow path. This reduces both short circuits and recirculation zones bringing the flow closer to the ideal plug-flow condition.

Comparisons of nitrite accumulation, microbial behavior and nitrification kinetic in continuous stirred tank (ST) and plug flow (PF) moving bed biofilm reactors

Two types of continuous stirred tank moving bed biofilm reactors (ST-MBBR) and plug flow MBBR (PF-MBBR) were compared for nitrification. PF-MBBR showed strong shock resistance to temperature, and ammonium oxidation ratio (AOR) was 9.63% higher than that in the ST-MBBR, although the average biomass and biofilm thickness of ST-MBBR were 7.32–18.59%, 9.44–14.06% higher than those in the PF-MBBR. Meanwhile, a lower nitrite accumulation ratio (NAR) was observed (54.88%) in the PF-MBBR than the ST-MBBR (78.92%) due to different operation modes, and the divergence was demonstrated by the microbial quantitative analysis. Nitrification kinetics revealed that the temperature coefficient (θ) in the ST-MBBR (1.068) was much higher than that in the PF-MBBR (1.006–1.015), proving the contrasting nitrification performances caused by temperature shock. According to the Monod equation, the half-saturation coefficient (KN) in the ST-MBBR was 0.19 mg/L while it varied around 0.12–0.24 mg/L in the PF-MBBR, revealing various NH4+ affinity owing to different biofilm thickness and microbial composition. Finally, MBBR optimization related to operation mode, temperature, and free ammonium (FA) inhibition for nitrite accumulation was discussed.

Optimization and Analysis of a Slow-Release Permanganate Gel for Groundwater Remediation in Porous and Low-Permeability Media

Dense nonaqueous phase liquids (DNAPLs) like trichloroethylene (TCE) serve as the most common form of groundwater pollution in the world. Potassium permanganate (KMnO4) is a strong oxidant that can quickly destroy DNAPLs into innocuous products. Slow-release permanganate gel (SRPG), a mixture of colloidal silica (CS) and KMnO4, has been recently developed as novel treatment option for dilute and large plumes of DNAPLs in groundwater. The objective of this study was to characterize and optimize gelling and release properties of a SRPG solution in saturated porous media. It was hypothesized that CS and KMnO4 content of the SRPG constrain gelation and release duration. Batch and column tests showed that gelation could be delayed through manipulation of the KMnO4 content. In column tests, silica content had little effect on the gelation lag stage and release rate but influenced duration of permanganate release. Flow tank tests comparing Bindzil 1440 (B-40) SRPGs with pure KMnO4 solutions under varying media conditions demonstrated that the presence of CS enhanced lateral spread and prolonged release duration of the oxidant.

환경변화에 따른 바지락(Ruditapes philippinarum)의 반응 가시화

This study investigated find the respiration rate in accordance with the water temperature conditions and salinity by analyzing respiration pattern of philippinarum(Ruditapes philippinarum). We conducted to observe and record the flow of fluid by breathing in the target organism using PIV method. Philippinarum were placed in the experimental tank after stabilizing of water temperature and salinity. Recording was commenced when the tank flow was in static after putting particle into the tank. Laser generator was mounted on the side of experimental tank and camera on the front of the tank. the scattering of particles from the light source was recorded and the images were post-processed by software and analyzed results. At 15.1℃ and 27.0‰, the maximum turbulence intensity was 5,468×10SUP-6/SUP m/s. At 19.4℃ and 26.8‰, the maximum turbulence intensity was 26,357×10SUP-6/SUPm/s. Comparing the maximum turbulence intensity between the two experiments shows a difference of about 4.8 times.

Developing persulfate-activator soft solid (PASS) as slow release oxidant to remediate phenol-contaminated groundwater

The research objective was to develop a persulfate-activator soft solid (PASS) as a biodegradable slow-release oxidant to treat phenol-contaminated groundwater. PASS was prepared by graft copolymerization of acrylic acid (AA) and acrylamide (AM) onto 1% (w/v) sodium alginate mixed with 500 mg L−1 sodium persulfate and 5 mg L−1 ferrous sulfate. The physical and chemical properties of PASS were characterized using scanning electron microscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, differential scanning calorimetry, the water content and swelling ratio. Various variables, including the ratio of AA/AM, pH, temperature and the type of groundwater cations affecting PS release, were investigated. The maximum PS release in DI water was 98% in the ratio of PASS 1 (AA/AM, 75/25), 96% at pH 3, 83% at 25 °C, and 80% with Na+. The major factors controlling PS release were the AA/AM ratio and pH. PASS 1 can be stable in size and shape for 6–8 days and completely degraded within 34 days. The degradation rates of 10 mgL−1 phenol using PASS produced the highest kobs values for each variable at a ratio of PASS 1 (k=0.1408 h−1), pH 7 (k=0.1338 h−1), 25 °C (k=0.1939 h−1), and Ca2+ (k=0.1336 h−1). The temperature of the groundwater was key to driving the reaction between PS and phenol. PASS 1 was applied in simulated phenol-contaminated groundwater via horizontal tanks containing Ottawa sand. The results indicated 93.2% phenol removal within 72 h in a narrow horizontal flow tank and 41.7% phenol removal in a wide horizontal flow tank with aeration.

The relationship between soil nitrate distribution and growth rate of Capsicum frutescens in subsurface flow constructed wetland integrated with household septic tank

Domestic wastewater treatment unit consisted of a single chamber septic tank and Subsurface Flow Constructed Wetland (SFCW) was built in Yogyakarta, Indonesia. SFCW played a significant role as secondary treatment of septic tank effluent. This study aimed to analyze the soil nitrate and its distribution in sand layer of SFCW. The SFCW had a depth of 0.2 m of coral and sand layers with two leach pipes that were installed in the depth of 0.3 m along the garden and planted with chili (Capsicum frutescens). Soil nitrate content of SFCW and plant growth were analyzed for 8 weeks of observation. Soil samples were taken in different direction, both vertical and horizontal. In vertical direction, samples were taken with three different depth (10, 15, and 20 cm) from the surface. In horizontal direction samples were taken with three different distance from outlet pipe. Soil nitrate obtained in vertical direction was significantly different (P<0.005) with soil nitrate at the depth of 20 cm was higher than 15 cm and 10 cm. However, the soil nitrate obtained in horizontal direction was not significant (P>0.05). The soil nitrate has positive correlation with plant growth, the higher soil nitrate will increase the plant growth.

Dynamic response analysis of submerged floating tunnel - canyon water system under earthquakes

Submerged Floating Tunnel (SFT) is one new type of infrastructure, representing a challenge in structural engineering, both on the theoretical and operational fields. Several research work focused on this innovative structure, especially on effects of dynamic loadings such as earthquakes and sea waves. So far, the dynamic response of SFT under vertical seismic ground motion input and secondary hydrodynamic pressure has been studied deeply using theoretical and numerical methods. However, the dynamic response characteristics of SFT-Canyon water system under surging caused by the canyon horizontal sloshing motion remain unclear. In this paper, a new mathematical model for analyzing the dynamic response characteristics of SFT-Canyon water system caused by horizontal sloshing motion was proposed, which considered the transmission effect of canyon water to the original horizontal seismic wave input. Firstly, the canyon was simplified as a rectangular water tank and hydrodynamic potential flow theory was used to study the dynamic input to SFT through canyon water. After that, based on the theory of structural dynamics, SFT was simplified as an elastic support beam, and the action of horizontal seismic input was considered as the load transmitted through the fluid in the canyon to study the response of SFT transmitted through water. Finally, we used verified MATLAB coding to achieve Duhamel integration to solve the mathematical model of the system dynamic response under the action of sine wave and seismic wave respectively. Besides, the factors affecting the maximum vertical displacement response of SFT under hydrodynamic pressure caused by horizontal seismic input to the canyon were discussed.

Modelling and numerical simulation of the transport phenomena in water thermal energy storage tanks

Mathematical model for numerical simulation of the transient heat transfer and fluid flows in water thermal energy storage tanks is developed. The model allows analysis of the thermal fields in the accumulators at different schemes and modes of charging and discharging. It was verified and validated based on experimentally obtained information about the temperature stratification at charging of a thermal accumulator at a laboratory solar system. The proposed approach for numerical study of the thermal energy storage is convenient for parametrical estimation and improvement of the efficiency of the thermal systems.

Comparison of Efflux Time between Cylindrical and Conical Tanks Through an Exit Pipe

Mathematical equations for efflux time during gravity draining of a Newtonian liquid (below its bubble point) from large open storage tanks of cylindrical and conical shapes (Where the flow in the respective tanks is essentially laminar) through an exit pipe of same length and cross sectional area (the flow in the exit pipe line being turbulent) located at the bottom of the respective storage tanks are developed. The equations are ultimately simplified and written in dimensionless forms. These equations will be of use in arriving at the minimum time required for draining the contents of the respective geometries of storage vessels. To drain the same volume of liquid, the efflux time equations so developed are compared to find out which of the tanks considered drain faster.

Remediating Contaminated Groundwater with an Aerated, Direct-Push, Oxidant Delivery System

One of the biggest challenges to treating contaminated aquifers with chemical oxidants is achieving uniform coverage of the target zone. In an effort to maximize coverage, we report the design and installation of a novel aerated, slow-release oxidant delivery system that can be installed by direct-push equipment. By continuously bubbling air beneath a slow-release oxidant in situ, an airlift pump is created that causes water and oxidant to be dispersed from the top of the outer screen and drawn in at the bottom. This continuous circulation pattern around each drive point greatly facilitates the spreading of the oxidant as it slowly dissolves from the wax matrix (i.e., oxidant candle). Given that the aeration rate controls the outward flow of oxidant from the outer screen in all directions, the radius of influence around each drive point is largely a function of the outward velocity of the oxidant exiting the screen and the advection rate opposing the upgradient and lateral spreading. Temporal sampling from three field sites treated with the aerated oxidant system are presented and results show that contaminant concentrations typically decreased 50–99% within 6–9 months after installation. Supporting flow tank experiments that demonstrate oxidant flow patterns and treatment efficacy are also presented.

Analysis of land-based circular aquaculture tank flow field using computational fluid dynamics (CFD) simulation

Analysis of land-based circular aquaculture tank flow field using computational fluid dynamics (CFD) simulation

The Finite Element Numerical Investigation of Free Surface Newtonian and Non-Newtonian Fluid Flows in the Rectangular Tanks

In this paper, we develop a new computational framework to investigate the sloshing free surface flow of Newtonian and non-Newtonian fluids in the rectangular tanks. We simulate the flow via a two-phase model and employ the fixed unstructured mesh in the computation to avoid the mesh distortion and reconstruction. As for the solution of Navier–Stokes equation, we utilize the SUPG finite element method based on the splitting scheme. The same order interpolation functions are then used for velocity and pressure. Moreover, the moving interface is captured via the concise level set method. We take advantage of the implicit discontinuous Galerkin method to handle the solution of level set and its reinitialization equations. A mass correction technique is also added to ensure the mass conservation property. The dam break-free surface flow is simulated firstly to demonstrate the validity of our mathematical model. In addition, the sloshing Newtonian fluid in the tank with flat and rough bottoms is considered to illustrate the feasibility and robustness of our computational scheme. Finally, the development of free surface for non-Newtonian fluid is also studied in the two tanks, and the influence of power-law index on the sloshing fluid flow is analyzed.

Measurement of Flux at Sediment–Water Interface Using a Seepage Meter under Controlled Flow Conditions

The accuracy of groundwater flux measurement using a seepage meter was evaluated through a series of laboratory experiments under controlled flow conditions. Simulated groundwater influx and outflux rates were measured using a seepage meter, and the results were compared with the known water flux rates in our controlled tank flow system. Differences induced by the use of two different types of collection bag (Types 1 and 2) were also evaluated. The slopes of the trend lines between the controlled influx rate and influx as measured by the seepage meter were 0.6669 (for Type 1 bag) and 0.8563 (for Type 2 bag), suggesting that the groundwater influx rate as measured by the seepage meter may be less than the actual rate. This may be due to the resistance of the collection bags and head loss induced at the tubing orifice. With respect to outflux measurement, the slopes of the trend line were 1.3534 (for Type 1 bags) and 1.4748 (for Type 2 bags), suggesting that the outflux rate as measured by the seepage meter may be more than the actual rate. The size and wall thickness of the collection bag used affected the measured flux rates. This study suggests that, as long as errors can be identified, seepage meters can be a reliable means of studying groundwater–surface water interactions.

Observation on sloshing flow and hydrodynamic pressures on cylindrical liquefied natural gas tank with swash bulkhead

In this study, a series of sloshing model tests were conducted for type-C tanks, particularly to observe the effects of the inner bulkhead and rings. In regular pitch motion, the internal flow by swash bulkhead and rings located inside the tank was observed. The frequency range near the resonance frequency was checked at filling heights of 70%, and sloshing-induced impact pressures were investigated. Through this study, the global flows inside the tank and local flows during impact occurrence at the hemispherical end of the tank were systematically observed, and the impact pressure pattern for each frequency ratio was compared. Due to the swash bulkhead located in the center of the tank, the flow does not move at once and the velocity of the flow is reduced by the inner rings. The flows passing through the swash bulkhead proceed with a time difference, overlapping with the first wave, generating various types of sloshing impact. The results of computational fluid dynamics calculation and the experiment were also compared for limited conditions.

Anaerobic digestion (AD) of fruit and vegetable market waste (FVMW): potential of FVMW, bioreactor performance, co-substrates, and pre-treatment techniques

Fruit and vegetable marketplace waste (FVMW) is an appealing alternative for energy production and should be utilized as a single substrate in anaerobic digestion (AD)–based biogas plants at an industrial-scale level in subtropical climatic countries. India alone generates 961,000 tons of FVMW annually from the major fruit and vegetable markets (FVMs). Utilization of FVMW to produce useful energy by AD could be helpful in meeting the ever-increasing energy demands of these countries. AD of fruit and vegetable waste (FVW) by two-phase systems has revealed good results in terms of stability, performance, and biogas generation; however, innovative approaches like plug flow tank reactor (PFTR) with passive solar heating with no mixing and no energy heating coupled with heat balance models and resistance network–based heat balance models need to be researched for subtropical climatic conditions in order to optimize the economics and energy balance of an AD system. Food waste and slaughter house wastes could be utilized successfully as co-substrates with FVW. C/N ratio is a critical performance parameter in the AD systems involving co-substrates; however, the synergistic relationship among co-substrates and characteristics, viz., macro- and micronutrients of individual co-substrates, must be investigated to improve the AD process. The optimum proportions of co-substrates could be determined by individual substrate characterization, biomethanation potential (BMP), and biodegradation kinetic models, thereby saving time and money as compared with random experimentation. Thermal, ultrasonic, and electrical pre-treatment in addition to physical pre-treatment could be effectively used for pre-treating FVW; however, synergy between co-substrates and pre-treatment method must be researched in order to justify the increased cost in extra pre-treatment.