Air Supply Inlet Research Articles

Optimal Determining Air Supply Humidity for Multi-Location Demands Under Different Objectives in an Indoor Moisture Environment: A Comprehensive Method and Case Study

Within high-precision indoor environments, such as semiconductor fabrication or textile plants, humidity control is paramount for preserving product integrity and reducing energy expenditure. The non-uniform indoor air environment poses a significant challenge in achieving humidity regulation that meets the distinct requirements of various locations. Traditional feedback control mechanisms may lead to instability, overshooting, and oscillation in indoor parameters. This paper proposes a comprehensive method to address humidity assurance issues in high-precision indoor environments by establishing analytical expressions that link the demand parameters at different locations with air supply parameters. Using a case study, this paper examines several typical operational scenarios with diverse control objectives, including minimizing dehumidification energy consumption, minimizing air supply humidity adjustment values, and constraints on adjustable air supply inlets. This method enables rapid calculation of air supply humidity and regulation of humidity parameters at multiple locations within the indoor environment. It considers various locations, requirements, optimization targets, and precision, demonstrating that it can quickly determine the optimal air supply parameters based on the objective function. This method facilitates rapid adjustment and high-precision assurance of different humidity requirements at multiple locations, making it suitable for high-precision design and control of indoor humidity environments.

Independent local environment control for visitor and relics area within site museums by displacement ventilation

The interior spaces of large-span site museums can typically be categorized into relic preservation areas, visitor corridors, and non-occupied spaces, with only the relic preservation areas and visitor corridors requiring environmental control. The conflicting needs of visitors and relics often render inefficiencies in simultaneously satisfying the thermal needs when using a sole environmental control system. To address this, an independent local environment control method that employs an air curtain to isolate the visitor corridor from the unoccupied space, along with displacement ventilation (DV) systems to regulate the local environment for the visitor corridor and relics, is proposed in this study. The effects of the supply air inlet and air curtain on the performance of the DV system and the feasibility of an independent local environmental control system were evaluated. The results indicated that the performance of the DV system in the visitor corridor was optimal when the height of the air inlet was 0.6 m. When both DV systems were operating, the mean temperature and relative humidity (RH) were 25.6 °C and 68.6 %, respectively, in the visitor corridor, and 20.6 °C and 95.3 %, respectively, in the relic preservation area; both visitor and relic requirements were met independently. This study provides a newly designed independent local environmental control system for museums.

Numerical Simulation of Airflow Velocity and Temperature Distribution in an Aircraft Cabin

In this work, a computational fluid dynamics (CFD) model is established to calculate the airflow distribution in the cabin of a single-channel Boeing 737-800 airplane. The RNG k-ε model, considering the calculation of turbulence kinetic energy and its rate of dissipation, is adopted to solve turbulence problems in physical field simulation. The proposed three-dimensional model is able to consider the particular physical factors and spatial structures, which can simulate the detailed distributions of complex physical fields, compared with the one-dimensional lumped parameter model. The velocity and temperature fields under different air supply velocities are then numerically investigated. The calculation results show that when the air velocity at the top air supply inlet is 1.4 m/s, the velocity and temperature distribution inside the cabin can both meet the comfort requirements of humans in the airworthiness standards. The results from this work can help to design an aircraft environmental control system.

Predicting indoor 3D airflow distribution using artificial neural networks with two different architectures

To meet the thermal comfort requirements of room occupants, a fast and accurate method for predicting indoor high-resolution 3D airflow distribution is necessary, which can be combined with heating, ventilation, and air conditioning (HVAC) systems to adjust the indoor environment. Artificial neural networks (ANN) can establish complex mappings between variables with nonlinear relationships. The aim of this study was to verify the feasibility of an ANN for the fast and accurate prediction of indoor 3D airflow distribution. Considering two prediction strategies, ANN A and B were constructed. The inputs of both ANNs were the air supply velocity, air supply direction, and section location. ANN A output the airflow distribution of the entire room directly, whereas ANN B output the airflow distribution of the characteristic sections first and then the airflow distribution of other sections according to the contribution of the characteristic sections. The two ANNs’ performances on training and testing datasets were compared. Both ANNs performed well in the training and interpolation cases. However, their performances decreased rapidly in the extrapolation cases. In the case of a large gap between the input and output dimensions of the ANNs, the two-step prediction strategy improved the prediction accuracy, accelerated convergence, and alleviated data imbalance problems. The prediction time of ANN A and B was 0.89 s and 12.38 s, respectively. The ANN can predict indoor high-resolution 3D airflow distribution quickly and accurately, and can add functions that include identifying internal heat sources and air supply inlet position changes. ANN combined with HVAC could allow real-time control to regulate indoor airflow.

Effect of physical partition height on medical staff exposure in a barn-integrated operating room

The barn-integrated operating room (BOR), is defined as an operating room where multiple surgical operating tables are located in the same room, and this type of operating room has an advantage of full and efficient use of medical human resources. However, contaminants (i.e., surgical smoke) will inevitably flow from the surgical zone to other zones, and thus increase the exposure risk of the staff. Such exposure risks have not been analyzed, and there is still a lack of study on measures to avoid mutual interference between different surgical zones remain unmentioned so far. Therefore, a numerical investigation is conducted on the difference in exposure risk of surgeons and circulating nurses in the BOR and COR (conventional operating room, which is an operating room with only one surgical operating table), and then identified the significant potential of physical partition with different heights to reduce infection risk. The results show that the personnel exposure risk in the BOR is higher than that in the COR, especially for the circulating nurses. When a physical partition is mounted on the supply air inlet, the inhalation concentration of surgical staff can be reduced evidently, whether there is one contaminant releasing area or two. In addition, to minimize the risk of personnel exposure in different surgical areas, the partition height is recommended to be 0.3 m–0.9 m.

Fast regulation of multi-position differentiated environment: Multi-step joint optimization of air supply parameters

It is necessary to maintain differentiated air parameters oriented to their desired values for objects at various positions. Parameter regulation at each target position is expected to be performed more rapidly. In this study, a multi-step joint optimization (MSJO) and regulation strategy is proposed for the fast regulation of multi-position differentiated parameters. A linear relationship under a fixed flow field is adopted to correlate the air parameters at each target position with various influencing factors in a non-uniform environment. Two air supply optimization models are established based on the linear relationship: one for the fast regulation of air parameters during the intermediate steps and the other for satisfying the desired parameters in the final step. Based on numerical analysis, MSJO is shown to be significantly superior to one-step optimization, and the parameter variation time for the single and two positions can be reduced by more than 70%. Even if the number of target positions exceeds that of the air supply inlets, the parameter at each position can be regulated to the vicinity of their desired values, and the parameter variation time can be reduced by at least 36%. The reverse regulation of parameters at the two target positions does not affect the acceleration of parameter variation, and MSJO can reduce the time by at least 32%. The proposed model-based air supply regulation strategy may serve as a reference for establishing a multi-position non-uniform environment.

Investigation into fresh air delivery performance with vortex ring

An air supply mode based on vortex ring structures was proposed to deliver fresh air for good indoor air quality. This study focused on the influence of air supply parameters, including formation time (T*), supply air velocity (U0), and supply air temperature difference (ΔT), on the fresh air delivery performance of an air vortex ring using numerical simulations. The cross-sectional average mass fraction of fresh air (Ca) was proposed to evaluate the fresh air delivery performance of the air vortex ring supply. The results showed that the convective entrainment of the vortex ring resulted from the combined effect of the induced velocity generated by the rotational motion of the vortex core and the negative pressure zone. When the formation time T* < 3.5, Ca increases with an increase in the formation time but decreases with an increase in the formation time for T* > 3.5. The variation in Ca is insignificant for U0 < 3 m/s or U0 > 3 m/s but decreases with an increase in the supply air temperature difference (ΔT). Thus, the optimal air supply parameters for air vortex ring supply are identified as T* = 3.5, U0 = 3 m/s, ΔT = 0 °C. Compared with the traditional circular and square free air jets, within 25Ds (Ds: the diameter of air supply inlet) downstream from the air inlet, the fresh air delivery performance of the air vortex ring supply is increased by a maximum of nearly 200 %, with an average improvement of approximately 120 %.

Defrosting Characteristics of the Cockpit Windshield of Manned Airships

Frost covering of the cockpit windshield will seriously obstruct the driver’s vision and even affect flight safety of the low-altitude manned airship. To solve the problem, this paper proposes a rapid defrosting strategy using hot gas injection method. The influences of the air inlet type, air temperature, air velocity and air angle on the defrosting characteristics of the transparent windshield are investigated and the defrost characteristics of the manned airship are obtained by fluid dynamics simulation. The result shows: (1) Defrosting effect of single inlet is not as good as double inlets. The defrosting area of the double inlet is relatively large, mainly concentrated at both ends of the windshield. (2) The effect of air supply temperature on defrosting effect of windshield surface is more significant when double air supply inlets are used. But when the air supply temperature reaches a certain value and continues to rise, the defrosting time does not change much, so there is an optimal air supply temperature range. (3) The higher the air supply velocity is, the shorter the phase transformation time of frost layer is and the faster the melting velocity is. Considering energy consumption and defrosting characteristics, the optimal air supply velocity is about 6 m/s. (4) When the angle between the air supply direction and the horizontal plane of the bridge near the windshield is 100°, the frost layer has the shortest melting time.

Effect of Air Inlet Spacing on Air Distribution and Ventilation Performance of Stratum Ventilation Using Multiple Parallel Jets

An appropriate layout of air terminals can improve the thermal comfort and air quality for room occupants. Stratum ventilation (SV) can efficiently provide thermal comfort and quality of inhaled air. However, investigations into the impact of the supply air inlet spacing on performance under SV are lacking. This study conducted experimental measurements and numerical simulations to analyze the effect of the supply inlet spacing on the air distribution and ventilation performance of the SV. Six theoretical axial velocity attenuation formulas were verified using experimental results. The effective draft temperature for SV (EDTS), air diffusion performance index (ADPI), the local mean age of air (LMAA), and energy utilization coefficient (EUC) were used as the evaluation indexes. The results indicated that the modified Abramovich formula was the most suitable for predicting the attenuation of the axial velocity of multiple parallel jets under SV. At an air supply spacing of 650 mm, the position near the central air supply inlet experienced a cold thermal environment with high air velocity and low air temperature; the positions on both sides of the room were warmer owing to insufficient airflow. The air distribution at these positions improved with increasing air inlet spacing, but some areas could not be covered by the supply airflow. The optimal value of ADPI corresponded to an air inlet spacing of 800 mm, whereas optimal LMAA and EUC corresponded to a spacing of 950 mm. Analysis of a multi-objective optimization method indicated that an air inlet spacing of 800 mm provided optimal overall performance.

Study on the one-dimensional governing equations of aerostatic circular thrust bearing with a single air supply inlet

PurposeThe purpose of this paper is to derive the one-dimensional governing equations to describe the pressure distribution, load capacity and stiffness of aerostatic circular thrust bearing with a single air supply inlet.Design/methodology/approachThe film flow field is divided into four regions: supply pressure region, pressure dropping region, pressure rising region and laminar flow region. The influences of bearing clearance and supply pressure on the pressure distribution, load capacity and stiffness of the bearing are presented.FindingsWith the large film clearance and large supply pressure, the oblique shock wave occurs near the entrance of gas film, which greatly increases the pressure drop region. Hence, it is not appropriate to consider the oblique shock as a normal shock.Originality/valueThis paper introduces the invariants at the entrance of gas film, employs the functional relationships between density and pressure, and provides the empirical formulas for the pressure dropping and rising regions. The pressure distribution curves are therefore illustrated through a considerably simplified computational process.

Is there a systematic hidden 'hot spot' in refrigerated containers filled with fresh food in ventilated packaging?

BackgroundThousands of refrigerated containers transport fresh fruit and vegetables to feed the world yearly. These containers should preserve fresh-food quality as uniformly as possible throughout the cargo. Scope and approachSeveral simulation studies have suggested the presence of a systematic hot spot in these containers near the supply-air inlet when warm cargo is cooled down in the container. Induced by airflow recirculation inside the ventilated packaging, the hot spot is located at the bottom of the pallets near the refrigeration unit. The fruit at the bottom of these pallets is well known to be exposed to cold air. However, the existence and impact of this apparent hot spot were not acknowledged explicitly. Interestingly, full-scale experiments and computational fluid dynamics (CFD) simulations contradict the existence of this recirculation-zone-induced hot spot. Key findings and conclusionsWe analyzed the literature and the physical phenomena at play to identify if and why this recirculation-driven hot spot occurs. We found that the airflow recirculation can be partially hidden in full-scale experiments and that we are often not looking for it at that location. Physically, the presence of the recirculation zone is plausible. The CFD simulations that predict this zone include all relevant physical processes. However, we still need proof by detailed full-scale experiments to confirm its existence. It is likely that the recirculation only occurs in some ventilated shipments, but then we need to identify for which shipments this happens. If this recirculation zone is present in a ventilated cargo of perishables, we need to solve this problem urgently. We suggest a roadmap with steps to do so. Otherwise, we would be systematically losing food quality in many shipped containers. Besides slowing down fruit cooling, such a recirculation vortex can trap respiration heat, moisture, and metabolic gases. Mitigating this hot spot thus can considerably impact the quality of the fruit and vegetables shipped worldwide.

Theoretical basis and method of airflow organization design in enclosed or semi-enclosed space

<p indent="0mm">The heating, ventilation, and air conditioning (HVAC) system is currently an important means to create a healthy and comfortable enclosed or semi-enclosed space environment, but the existing HVAC systems not only consume high energy, but also easily cause human health problems, such as sick building syndrome, building-related diseases, and cross infection of infectious diseases. The above phenomenon further shows that the indoor airflow organization (based on the traditional method) formed by the end of the HVAC system is still not perfect, and there are certain blind spots and deficiencies. To solve the problems existing in the design and use of the end of the traditional HVAC system, the inverse design method came into being. The traditional design method is a process of repeated trial and error, while the inverse design method uses an optimization algorithm to inversely determine the airflow organization form and thermophysical boundary (such as the number, shape, and size of air supply inlets and air supply parameters) that meet the needs or objectives by minimizing the objective function. The biggest difference from traditional methods is that the inverse design method can determine the optimal direction vector in each design cycle, while the traditional design method can only keep trial and error. To further clarify the differences between the two types of methods and promote the continuous improvement of inverse design methods, this paper first expounds the scientific problems faced by or to be solved in the construction of indoor environments. The core problem of indoor environment construction is to determine the appropriate airflow organization form and the key scientific problem behind the difficulty in quickly determining the appropriate airflow organization form is that it is difficult to obtain the analytical solution (essence) of the highly nonlinear N-S equation. Then, the classification of airflow organization design methods and their basic principles are introduced in detail. The design performance of the two types of methods is then demonstrated through real-world case results. Although the inverse design method has made great progress in the field of indoor environment construction, the current inverse design method still requires theoretical deduction, program development, and numerical solution, which hinder its popularization and application to a certain extent. Finally, this paper discusses the possible future development directions in the field of indoor environment construction. For example, with the rapid development of human factors engineering, inverse design methods, digital design methods, intelligent control, and other fields, indoor environment design and creation will tend to be diversified and intelligent.

Impact of ventilation and avoidance measures on SARS-CoV-2 risk of infection in public indoor environments

BackgroundThe literature includes many studies which individually assess the efficacy of protective measures against the spread of the SARS-CoV-2 virus. This study considers the high infection risk in public buildings and models the quality of the indoor environment, related safety measures, and their efficacy in preventing the spread of the SARS-CoV-2 virus. MethodsSimulations are created that consider protective factors such as hand hygiene, face covering and engagement with Covid-19 vaccination programs in reducing the risk of infection in a university foyer. Furthermore, a computational fluid dynamics model is developed to simulate and analyse the university foyer under three ventilation regimes. The probability of transmission was measured across different scenarios. FindingsEstimates suggest that the Delta variant requires the air change rate to be increased >1000 times compared to the original strain, which is practically not feasible. Consequently, appropriate hygiene practices, such as wearing masks, are essential to reducing secondary infections. A comparison of different protective factors in simulations found the overall burden of infections resulting from indoor contact depends on (i) face mask adherence, (ii) quality of the ventilation system, and (iii) other hygiene practices. InterpretationRelying on ventilation, whether natural, mechanical, or mixed, is not sufficient alone to mitigate the risk of aerosol infections. This is due to the internal configuration of the indoor space in terms of (i) size and number of windows, their location and opening frequency, as well as the position of the air extraction and supply inlets, which often induce hotspots with stagnating air, (ii) the excessive required air change rate. Hence, strict reliance on proper hygiene practices, namely adherence to face coverings and hand sanitising, are essential. Consequently, face mask adherence should be emphasized and promoted by policymakers for public health applications. Similar research may need to be conducted using a similar approach on the Omicron (B.1.1.529) variant.

Droplet aerosols transportation and deposition for three respiratory behaviors in a typical negative pressure isolation ward

Negative pressure isolation wards could provide safety for health care workers (HCWs) and patients infected with SARS-CoV-2. However, respiratory behavior releases aerosols containing pathogens, resulting in a potential risk of infection for HCWs. In this study, the spatiotemporal distribution of droplet aerosols in a typical negative pressure isolation ward was investigated using a full-scale experiment. In this experiment, artificial saliva was used to simulate the breathing behavior, which can reflect the effect of evaporation on droplet aerosols. Moreover, numerical simulations were used to compare the transport of droplet aerosols released by the three respiratory behaviors (breathing, speaking, and coughing). The results showed that droplet aerosols generated by coughing and speaking can be removed and deposited more quickly. Because reduction in the suspension proportion per unit time was much higher than that in the case of breathing. Under the air supply inlets, there was significant aerosol deposition on the floor, while the breathing area possessed higher aerosol concentrations. The risk of aerosol resuspension and potential infection increased significantly when HCWs moved frequently to these areas. Finally, more than 20% of the droplet aerosols escaped from the ward when the number of suspended aerosols in the aerosol space was 1%.

Demand-oriented differentiated multi-zone thermal environment: Regulating air supply direction and velocity under stratum ventilation

Different thermal preferences from occupants in a shared space must be satisfied simultaneously. For a ventilated room with multiple air supply inlets, differentiated thermal environment parameters can be maintained in different subzones by liberating the unified air supply parameter adjustment from all the air supply inlets and subsequently adopting independent adjustment of different groups of air supply inlets near different subzones. In this study, the achievable difference level of thermal environment was investigated numerically based on the stratum ventilation. Primarily, the effect of independently regulating the air supply directions and velocities from two inlet groups on the difference in the local thermal environment between subzones was analyzed. The position of occupants and heat distribution were considered as the influencing factors. Further, the predicted mean vote (PMV) index was utilized to evaluate the cool or warm degree of the local thermal environment while the draught rate (DR) and percentage dissatisfied (PD) indices were utilized to evaluate the local thermal discomfort. The results obtained indicated that regulating air supply direction significantly affected the differentiated thermal environment, with the achievable ΔPMV between subzones up to 1.46. Moreover, the increase in air supply velocity based on the appropriate air supply direction further expanded the ΔPMV. In addition, the change in heat source position resulted in a ΔPMV decrease of 0.36. No strong draught risk and local thermal discomfort caused by the vertical temperature difference were observed. This study is expected to provide guidance for the maintenance of demand-oriented zoning thermal environment.

The influence of air supply inlet location on the spatial-temporal distribution of bioaerosol in isolation ward under three mixed ventilation modes

The outbreak of COVID-19 and the spread of infectious pathogens through bioaerosols have once again aroused widespread concern worldwide. Isolation ward is an important place to prevent the spread of infectious bioaerosols. However, infection of health care workers (HCWs) in the isolation ward often occurs, so it is urgent to carry out relevant research to reduce the cross-infection between HCWs and patients. In this paper, the temporal and spatial distribution characteristics of bioaerosols under three mixed ventilation modes in a single ward were studied, namely, upper supply side return air of Case 1 and side supply and side return ventilation are Case 2 and Case 3 respectively. The results show that the removal efficiency of bioaerosol in the ventilation mode of Case 3, in which directional airflow is formed from the air supply inlet to the release source and then to the exhaust outlet, is 46.6% and 67.7% higher than that of Case 1 and Case 2, respectively. In addition, ventilation methods based on mixed theory do not guarantee good air quality in the breathing zone (1.3 m to 1.7 m) of HCWs, which may increase the inhalation risk for HCWs. It is hoped that our results can provide some useful suggestions for optimizing the airflow layout of the isolation ward, reducing the risk of cross-infection, and virus elimination.

Regression Models for Performance Prediction of Internally-Cooled Liquid Desiccant Dehumidifiers

In this study, using response surface methodology and central composite design, regression models were developed relating 12 input factors to the supply air outlet humidity ratio and temperature of 4-fluid internally-cooled liquid desiccant dehumidifiers. The selected factors are supply air inlet temperature, supply air inlet humidity ratio, exhaust air inlet temperature, exhaust air inlet humidity ratio, liquid desiccant inlet temperature, liquid desiccant concentration, liquid desiccant flow rate, supply air mass flow rate, the ratio of exhaust to supply air mass flow rate, the thickness of the channel, the channel length, and the channel width of the dehumidifier. The designed experiments were performed using a numerical two-dimensional heat and mass transfer model of the liquid desiccant dehumidifier. The numerical model predicted the measured values of the supply air outlet humidity ratio within 6.7%. The regression model’s predictions of the supply air outlet humidity ratio matched the numerical model’s predictions and measured values within 4.5% and 7.9%, respectively. The results showed that the input factors with the most significant effect on the dehumidifying process in order of significance from high to low are as follows: supply air inlet humidity ratio, liquid desiccant concertation, length of channels, and width of channels. The developed regression models provide a straightforward means for performance prediction and optimization of internally-cooled liquid desiccant dehumidifiers.

Local attachment ventilation system for the unearthed relic preservation area within site museum

Environmental control of relic preservation areas in site museums with large exhibition halls is attracting growing interest. Local environmental control systems, such as displacement ventilation, can provide a suitable preservation environment in these museums with low energy consumption. However, the positioning of the air supply inlet at the bottom of the preservation area is not always feasible, because historical sites generally comprise the entire excavation area. This study proposes the use of an attachment ventilation system, which installs the air inlet and outlet at the top of opposite walls, as a more effective local environmental control system for the preservation of unearthed relics in funerary pits. Experiments were conducted in an experimental exhibition hall to evaluate the feasibility of this system. The diurnal temperature fluctuation of the preservation area decreased from 4.5 ℃ when the system was off to 1.7 ℃ when the system was on, and the corresponding temperature difference between the surrounding soil and air of relics decreased from 1.6 °C to 0.3 °C, thereby establishing a stable soil–air environment. These results demonstrate that attachment ventilation is an effective local environmental control strategy for the preservation of unearthed relics in site museums.

PIV experimental study of airflow structures in a multi-slot ventilation enclosure with opposed jets

The airflow structure of enclosure directly affects the spread of COVID-19 and is also closely related to indoor air quality, thermal comfort of personnel, and building energy consumption. Although a large number of studies on the airflow field have been conducted under mixing and displacement ventilation with a single air inlet in rectangular rooms. However, to the best of the authors knowledge, only a limited number of studies have dealt with airflow structures in a multi-slot ventilation enclosure with opposed jets. Therefore, this paper uses PIV to study the velocity and entropy of unstable airflow field in a multi-slot ventilation enclosure with opposed jets under isothermal and non-isothermal conditions. And this paper presents due to the collision of the jets to form two large-scale eddies, the airflow field structure being unstable. In the region without air supply inlets and exhaust outlets, a large-scale vortex is formed in the airflow field, resulting in high information entropy of the flow field. The thermal plume suppresses the large-scale flow field structure and increases the small-scale flow field structure.

The effects of room length on jet momentum flux

As to mixing ventilation in indoor environments, the turbulent jet plays a major role in driving the air movement, contaminant transport, and heat transfer. The main characteristic of a turbulent jet is its momentum flux. By entrainment of air, the flow of a jet increases and may enhance the flooding of contaminant. In investing the jet’s momentum flux, it is generally regarded that the supply jet collides with the opposing wall and the jet is transformed into a wall jet. However, this is not always true if a jet is not sufficiently strong, or the length of a room is large. Therefore, this study adopted computational fluid dynamics (CFD) to investigate the supply jet development and its momentum flux by varying the room length. Initially, the width of the air supply inlet was the same with that of the room. By defining n as the ratio of room length and height, when n = 3, there is a horizontal a vortex which is the normal behaviour. When the room length increased further, the supply jet was unable to collide with the opposing wall. This investigation got two vertical vortices at the room end which is new. The two new vertical vortices were most pronounced for n = 5. It is possible that increasing the length of the room introduces a gradual transition towards a flow in a rectangular duct. This flow is probably very much governed by the side walls. Therefore, this study reduced the width of the air supply inlet by half and maintained the same flow rate. However, a single vertical vortex was identified at the room end for n = 5. In both scenarios, the supply jet may create new vortices that would enhance the flooding of contaminants.