Surface Spray Research Articles

Can air nanobubbles improve the swim bladder inflation in developing European perch? A pilot study of advanced water treatment.

Swim bladder inflation (SBI) is a fundamental step in larval development for both physostome and physoclist fish species. Failure of the SBI triggers higher energy expenditures of the individual, which negatively affects swimming ability, growth rate, feeding efficiency, susceptibility to predation, and survival rate. In aquaculture, the SBI failure is caused by different factors including: (a) water contamination with oil increasing the surface water tension and preventing the larvae from gulping air bubbles for inflation, and (b) bacterial aerocystitis of the swim bladder caused by gulped organic debris. Hence, novel and effective water treatment technologies such as nanobubbles can be employed in aquaculture to reduce the risk of low SBI. In the present study, we compared conventional water treatment, i.e. surface spray combined with skimmers with air nanobubbles either alone or in combination, on the SBI of European perch larvae. In the control, no water treatment technology was employed. All treatments showed higher SBI efficiency compared to the control. The control group showed the lowest percentage of swim bladder-inflated individuals associated with low body weight (BW). The highest BW and SBI efficiency was recorded with the combination of surface skimmer, spray, and nanobubbles. The current study offers the first investigation of the nanobubbles' effect on SBI promotion in larvae of European perch and gives motivation for future optimizations.

Study on Corrosion Damage Behavior of 300M Ultra-high Strength Steel in Marine Atmospheric Environment

Abstract The marine atmospheric environment exposure test of 300M ultra-high strength steel was carried out at Hainan test station. The corrosion damage behavior of 300M ultra-high strength steel in marine atmospheric environment was studied by macroscopic and microscopic corrosion morphology, tensile properties and stress corrosion. The results show that the comprehensive corrosion behavior of 300M ultra-high strength steel occurred in the marine atmospheric environment. The color of the corrosion products changed from red to reddish brown, dark brown and black, and the maximum corrosion depth in the three years was 400μm. The corrosion had a significant effect on the tensile properties during the test. The tensile strength and elongation of 300M ultra-high strength steel decreased by 13.3 % and 81.8 %, respectively, which indicated that the effect of corrosion on the plasticity of the material was much greater than that on the tensile strength. Corrosion also caused a decrease in fracture toughness, and the fracture toughness of 300M ultra-high strength steel decreased by 26% in 2 years. The results of stress corrosion show that the crack propagation of 300M ultra-high strength steel is very rapid in the initial stage of marine atmospheric environment test, and the crack propagation length reaches 10.836mm in 7 days. The stress corrosion threshold KISCC of 300M ultra-high strength steel is 24.48MPa•m1/2, and the relative index of stress corrosion cracking sensitivity is 0.31, which indicates that 300M ultra-high strength steel is very sensitive to stress corrosion in marine atmospheric environment. The results show that 300M ultra-high strength steel has poor adaptability to the marine environment. Therefore, it is necessary to adopt excellent surface treatment process and spray aging resistant coating to effectively protect 300M ultra-high strength steel to ensure its long-term reliable use in the marine environment.

Verification of On-Site Applicability of Rainwater Road Surface Spraying for Promoting Rainwater Utilization and Analyzing the Fine Dust Reduction Effect

This study conducted a pilot test and field demonstration to analyze the feasibility of using rainwater for road surface sprinkling and its effectiveness in reducing fine dust to create sustainable cities. The pilot test results verified the effectiveness of rainwater sprinkling on road surfaces in reducing fine dust. Subsequently, to ensure field applicability, a test bed with different pavement sections was established along Ojeong-ro in Bucheon, Gyeonggi-do, and a circulatory system for reusing the runoff rainwater was installed and tested for its acceptable dust reduction effectiveness. The results showed that the section with porous pavement exhibited a significant reduction in acceptable dust levels, and a trend of decreasing pollutant levels due to the initial washing effect of rainwater was observed. However, the water quality and quantity analysis revealed that additional purification processes are necessary to reuse the water for road surface sprinkling. Based on these findings, this study suggests that expanding porous pavement and introducing purification systems are essential for installing rainwater utilization facilities to reduce fine dust in urban areas. This research provides critical foundational data that can contribute to urban environmental improvement and establish a sustainable water circulation system.

Formation of hydrophobic membranes by surface spray assisted NIPS: Effects of solvent/non-solvent and spraying conditions

Membrane distillation has long been a potential desalination technology. Recently, spray-assisted non-solvent induced phase inversion (SANIPS) was proposed as a facile and effective method to prepare microporous hydrophobic membranes for membrane distillation. However, the membrane formation process is not fully disclosed. In this paper, SANIPS is employed to fabricate hydrophobic PVDF membranes. The influencing factors on membrane structure and performance are investigated. Membrane structure is greatly affected by the choice of solvent and non-solvent spray. The interactions between different non-solvent sprays (water and ethanol) and solvents (TEP, NMP and DMF) and the effects of operating conditions on membrane formation are explored. Thermodynamic and kinetic analyses of the membrane formation process suggest that the membrane formation process is dominated by the kinetic factors with water being the spray while thermodynamic factors play the major role with ethanol being the spray. A hydrophobic membrane with water contact angle of 135.93 ± 4.38° and LEP of 2.5 ± 0.4 bar was successfully prepared by using ethanol as the non-solvent spray, which demonstrates a stable desalination performance (initial flux of 19.88 ± 1.39 kg·m−2·h−1 and salt rejection higher than 99.97 %) in vacuum membrane distillation. This study may provide pertinent insights into the rational control of membrane structure and performance of hydrophobic PVDF membranes.

A multi-nozzle nebuliser does not improve tissue drug delivery during PIPAC

BackgroundMulti-nozzle nebulisers for pressurised intraperitoneal aerosol chemotherapy (PIPAC) are implemented in clinical practice to improve the homogeneity of tissue drug delivery. Nonetheless, the advantages of such devices over one-nozzle nebulisers have not been demonstrated thus far. In this study, we compared the performance of multi- and one-nozzle nebulisers by conducting physical and ex vivo pharmacological experiments.MethodsThe one-nozzle nebuliser Capnopen® and the multi-nozzle nebuliser were the subjects of this study. In physical experiments, the aerosol droplet size was measured by laser diffraction spectroscopy. Spatial spray patterns were depicted on blotting paper. Pharmacological experiments were performed on the enhanced inverted bovine urinary bladder model, demonstrating real-time tissue drug delivery, aerosol sedimentation and homogeneity of doxorubicin and cisplatin tissue distribution.ResultsThe multi-nozzle nebuliser had a sixfold greater aerosolisation flow and a threefold greater angle of aerosolisation than Capnopen®. The aerosol particle size and distribution range were higher than that of Capnopen®. Spray patterns on blotting paper were more extensive with the multi-nozzle nebuliser. Real-time tissue drug delivery with the multi-nozzle nebuliser was over 100 ml within 1 min, and the aerosol sedimentation was 48.9% ± 21.2%, which was not significantly different from that of Capnopen®. The doxorubicin and cisplatin tissue concentrations were greater with Capnopen®. Although there was no significant difference in the homogeneity of doxorubicin distribution between the two devices, the homogeneity of cisplatin distribution was significantly higher with Capnopen®.ConclusionThe multi-nozzle PIPAC nebuliser did not fulfil expectations. Even though the surface spray patterns were broader with the multi-nozzle nebuliser, the tissue drug homogeneity and concentration were greater with Capnopen®.Graphical

Research and application of surface spray anti-corrosion technology for coiled tubing in pressurized environment

In this study, the corrosion risk of coiled tubing under high pressure, high temperature and high sulfur conditions was investigated, and the protection solution was put forward. In this paper, spray paint is used to prevent corrosion of tubing, and the effects of high temperature desulfurization and nano super absorbent spraying agent are compared. The pressure jet spraying device is designed for uniform spraying during operation to improve corrosion resistance. Determine the best spraying position and monitoring point. The results show that nano-coating agent can prevent cracking and serious corrosion, and its application effect in oil wells meets the requirements. These findings support that anti-corrosion spraying technology on coiled tubing surface can effectively prevent tubing corrosion in high temperature, high pressure and corrosive environment.

Tank-Mix Adjuvants Enhance Pesticide Efficacy by Improving Physicochemical Properties and Spraying Characteristics for Application to Cotton with Unmanned Aerial Vehicles.

Tank-mix adjuvants have been used to reduce spray drift and facilitate the efficacy of pesticides applied with unmanned aerial vehicles (UAVs). However, the effects of specific adjuvants on pesticide characteristics and the mechanism of action remain unclear. Herein, we analyzed the effects of three different types of tank-mix adjuvants (plant oil; mineral oil; and mixture of alcohol and ester) on the surface tension (ST), contact angle, wetting, permeation, evaporation, spray performance, and aphid-control effects of two types of pesticides. The mineral oil adjuvant Weichi (WCH) was highly effective in reducing the pesticide solution ST, improving the wetting and penetration ability, increasing droplet size, and promoting droplet deposition. The mixed alcohol and ester adjuvant Quanrun (QR) showed excellent wetting and antievaporation properties and promoted droplet deposition. A plant oil adjuvant (Beidatong) moderately improved wetting and penetration ability and reduced droplet drift. Field tests showed that the control efficiencies (CEs) of two pesticides were increased after the addition of adjuvants, even with 20% reductions in pesticide application. When the UAV was operated at 1.5 m, the CEs of two pesticides were increased from 65.39 and 66.63% to 73.11-76.52% and 77.91-88.31%, respectively. When operated at 2.5 m, the CEs were increased from 51.24 and 68.60% to 65.06-75.70% and 77.57-92.59%, respectively. Especially, the CEs of pesticides with WCH and QR increased obviously. Importantly, neither WCH nor QR inhibited hatching of the critical insect natural enemy ladybird beetle at concentrations used in the field. This study provides a framework for assessment of tank-mix adjuvants in aerial sprays and directly demonstrates the value of specific adjuvants in improving pesticide bioavailability and minimizing associated environmental pollution.

Agitation inside the Liquid Film on Two-Fluid Jet Sprayed Surface

Agitation inside the Liquid Film on Two-Fluid Jet Sprayed Surface

Climate impact, toxicological risks and economic efficiency of conventional and new weed control methods in sugar beet

The aim of this study was to assess the toxicological risks, the climate impact and the economic efficiency of conventional and new weed control methods with reduced herbicide use. For this purpose, i) resource consumption, CO2 emissions, number of field work days, costs and labor hours were calculated for 11 weed control methods; ii) the toxicological risk for non-target organisms was modeled for 4 methods with reduced herbicide use and for conventional spraying with SYNOPS-GIS. The results showed that no method is fully environmentally friendly. Although the use of the FarmDroid hoeing robot is toxicologically harmless, it is disadvantageous in terms of CO2 emissions and overall costs compared to broadcast spraying. Equipping a FarmDroid with spot spraying would reduce the toxicological risk by 90% and CO2 emissions by 5% compared to conventional broadcast spraying. The costs would be only slightly higher than for conventional surface spraying. Although the new CONVISO method has the highest aquatic toxicity, it is the most favorable in terms of climate friendliness, energy consumption, terrestrial toxicity and cost-effectiveness.

Efficiacy test of insectiside with pirimiphos-methyl and alpha-cypermethrin on Musa domestica using surface spraying method

Abstract The bacteria are in human food through insects that act as disease vectors, such as flies. The housefly (Musa domestica) is one of the insects around human habitation that can affect human health. Therefore, controlling the M. domestica population must be done to prevent disease transmission, such as using insecticide. This research used the pirimiphos-methyl and alpha-cypermethrin active ingredients with different doses applied using the surface spraying method of the paper. Then, it was smeared with honey as an attractant. Methods used in this research include test insect preparation, active ingredient application, and data analysis. The data were analyzed statistically using the one-way ANOVA test. Innovation of the research that comperation about active ingredients of the pirimiphos-methyl and alpha-cypermethrin. Result of the research, insecticides with the pirimiphos-methyl proved effective to controlling M. domestica with doses of MP2 and MP3 to 100% mortality in less than 8 hours. In comparison, for the alpha-cypermethrin active ingredient, the mortality of M. domestica is less than 90%. These results indicate that M. domestica in that area is resistant to the alpha-cypermethrin. This research can be used for pest control to control pests effectively and efficiently.

Enhanced Pool Boiling Heat Transfer with Porous Ti-6Al-4V-Coatings Produced by Cold Spray Metal Additive Manufacturing

In advancing industrial heat transfer mechanisms, surface coatings offer significant potential. This research elucidates the efficacy of the metal additive manufacturing Cold Spray deposition technique for producing enhanced boiling surfaces, specifically focusing on Ti-6Al-4V (Ti64) coatings on Aluminium substrates. This offers a rapid and low-cost fabrication method for producing lightweight enhanced boiling surfaces. The Cold Spray method is typically used to create dense metal deposits. Here, the process has been specially tuned to create highly inhomogeneous honeycomb-type porous Ti64 coatings. Critical Cold Spray deposition parameters, such as particle velocity, preheat temperature, and deposition rate have been identified to create repeatable porous coatings, with thicknesses of up to 3.0 mm achievable. Following deposition, several samples were subjected to systematic boiling heat transfer tests in a purpose-built pool boiling apparatus. Boiling curves were generated for the augmented Cold Spray surfaces as well as a bare surface, with the latter acting as a baseline to which enhancement levels were assessed. Initial data analysis shows that some of the tested surfaces exhibit a notable increase in boiling heat transfer coefficient and Critical Heat Flux (CHF). This enhancement is potentially attributed to increased surface area, increased nucleation site density, capillary wicking, and mitigation of lateral bubble coalescence, though excessive coating thickness may degrade heat transfer. In summary, the novel Ti64 surface structures developed using the Cold Spray deposition technique exhibits high potential for industries necessitating superior boiling heat transfer performance. Importantly, the manufacturing process is industrially scalable, offering the capacity to rapidly coat large areas at low cost compared with subtractive manufacturing other metal additive manufacturing methods.

Improvement of Global Forecast of Tropical Cyclone Intensity by Spray Heat Flux and Surface Roughness

AbstractIn global forecasting systems, tropical cyclone (TC) intensity is usually underestimated, which is one of the major challenges for TC forecasting. One possible reason is the deficiency of physical parameterizations associated with ocean surface waves. To improve the TC intensity forecast, effects of two powerful wave‐related processes, the spray‐mediated heat flux and surface roughness, are considered in a global coupled ocean‐atmosphere‐wave system (CFSv2.0‐WW3). Serial 24 hr forecasting experiments for all TCs from May to October 2019 are conducted, and comparisons are made against the International Best Track TC data. The results show that for strong TCs the underestimation of TC intensity in CFSv2.0‐WW3 is significantly improved by the modified surface roughness parameterization and the accelerated spray heat flux parameterization based on Gaussian Quadrature. For major hurricanes with initial wind speeds above 30 m/s, the error of TC maximum wind speed decreases by about 34.4%. To understand the associated dynamic and thermodynamic processes, a series of 120 hr simulations for major hurricane Hagibis is conducted. The effect of spray‐mediated heat flux accounts for 91.7% of the TC intensity improvement. The increased heat fluxes offset the negative contributions of vertical advection and ventilation, leading to enhanced entropy. The low‐level pressure is then decreased, resulting in enhanced convergence of absolute vorticity, which overpowers the negative effects of frictional dissipation and vertical momentum advection. The study indicates that the application of these two wave‐related parameterizations can potentially improve the global forecast and reanalysis of TC intensity.

Fabrication and Corrosion Resistance of Al-Co-Ce Amorphous Alloy Coating by a Combined Process of Thermal Spraying and Pulsed Electron Beam Surface Remelting

Fabrication and Corrosion Resistance of Al-Co-Ce Amorphous Alloy Coating by a Combined Process of Thermal Spraying and Pulsed Electron Beam Surface Remelting

A multifunctional cellulose paper with excellent flame retardancy, hydrophobicity and oil/water-separation performance via reaction with ammonium phytate and poly(methylhydrosiloxane)

Paper-based materials have become increasingly prevalent in the packaging and daily life. However, paper is flammable and hydrophilic, hindering its widespread application. Here, a novel reactive flame retardant of m-xylylenediamine phytate ammonium (MPAP) was prepared. Cellulose paper with superior flame-retardant and hydrophobic properties was successfully prepared by surface spraying technology and impregnation process, through the reaction of flame retardant and poly(methylhydrosiloxane) (PMHS) with cellulose fibers. The water contact angle (WCA) of the modified paper was 122.6°, while the limit oxygen index (LOI) value reached 41 %, which had significant self-extinguishing performance. The total heat release rate of the modified paper was reduced from 12.8 kJ/g to 0.6 kJ/g. The modified paper also exhibited excellent performance for oil/water separation. Furthermore, this effective and simple strategy can also be applied to other cellulose-contained substrates for the application in construction, textiles, furniture and other fields.

Surface Modification of 42CrMo Steels: A Review from Wear and Corrosion Resistance

This work reviews surface modification techniques for improving the wear and corrosion resistance of 42CrMo steel. The advantages and disadvantages of various methods, including thermal spraying, deposition, hardfacing, laser cladding, nitriding, and laser surface treatment, are discussed. The review elaborates on the materials commonly employed in laser cladding technology, including iron-based, cobalt-based, nickel-based, and high-entropy alloys and reinforced composite coatings. Furthermore, the mechanisms and methods of improving the wear and corrosion resistance of 42CrMo steel are summarized. Finally, this review presents research shortcomings and future opportunities of surface modification techniques. This review also provides a theoretical guide for the application of 42CrMo steel.

Carbon fiber reinforced composites with self‐sensing and self‐healing capabilities enabled by CNT‐modified nanofibers

AbstractCarbon fiber reinforced polymer (CFRP) composites with self‐sensing and self‐healing capabilities was developed in this work. Uniform dispersion of CNTs within a core‐shell nanofiber structure was achieved through a combination of electrospinning and subsequent surface spraying of CNTs. The resulting core‐shell nanofibers were incorporated into CFRP composites using a vacuum‐assisted resin transfer molding process. Mechanical testing demonstrated improved mechanical properties in the composites treated with CNT spraying. Real‐time, precise monitoring of structural damage was enabled through the measurement of electrical signal changes caused by composite deformation in static loading experiments. Furthermore, self‐healing experiments demonstrated that the thermally conductive network formed by CNTs facilitated more uniform heat transfer within the composites. During the healing process, resistive heating of damaged specimens was applied, resulting in a remarkable healing efficiency of 95.2%. The experiments indicate that the composite developed in this paper possess excellent self‐sensing and self‐healing capabilities.Highlights Damage self‐sensing and self‐healing CFRP composites were developed. CNTs‐modified nanofibers were applied to endow the composite specific abilities. Resistivity signals were collected for real‐time damage monitoring. The self‐healing efficiency of the designed composite reached up to 95.2%. Self‐sensing and self‐healing occurred autonomously within closed‐loop structure.

Dynamic Numerical Simulation of Curved Surface Coating Trajectory Based on STL Slicing Algorithm

The thickness of the coating on the surface of a workpiece is an important factor in determining the quality of spraying. However, it is challenging to estimate the distribution of film thickness accurately before the actual spraying process. This lack of estimation hinders the optimization of spraying process parameters and trajectory. To overcome this, a numerical simulation of surface spray coating thickness was conducted to provide guidance for the actual coating process. The research consists of three main parts. Firstly, the spray trajectory of the spray gun is determined using the proposed Stereo Lithography (STL) model slicing algorithm. Secondly, a two-phase flow spray model and collision adhesion model are established to construct the spray film model. The surface mesh is determined, and the spraying process parameters are set. Finally, numerical simulation is conducted to analyze the dynamic spraying trajectory and the distribution of coating thickness. The results show that the coating thickness distribution on an arc surface is thicker in the middle and thinner on the edges. The distribution is symmetric with respect to both the transverse and longitudinal directions of the arc surface. The coating thickness distribution at both ends is not as uniform as in the middle section. The concave part of the free surface has the largest coating thickness, while the coating thickness distribution on the convex part is not as uniform as on the relatively flat part. This method of simulating the coating thickness distribution on complex surfaces provides a solid foundation for further optimization of spraying process parameters and trajectory, ultimately improving the qualification rate of workpiece spraying processing.

Comparative analysis of the Potter Tower and a new Track Sprayer for the application of residual sprays in the laboratory

BackgroundEfforts to evaluate the residual efficacy of new indoor residual spraying (IRS) formulations have identified limitations with the industry standard laboratory sprayer, the Potter Spray Tower (PT). Calibrating the PT can be time-consuming, and the dosing of surfaces may not be as accurate or uniform as previously assumed.MethodsTo address these limitations, the Micron Horizontal Track Sprayer with Spray Cabinet (TS) was developed to provide higher efficiency, ease of operation and deposition uniformity equal to or better than the PT. A series of studies were performed using a fluorescent tracer and three IRS formulations (Actellic® 300CS, K-Othrine WG250 and Suspend PolyZone) sprayed onto surfaces using either the PT or the TS.ResultsDeposition volumes could be accurately calibrated for both spray systems. However, the uniformity of spray deposits was higher for the TS compared to the PT. Less than 12% of the volume sprayed using the PT reaches the target surface, with the remaining 88% unaccounted for, presumably vented out of the fume hood or coating the internal surfaces of the tower. In contrast, the TS deposits most of the spray on the floor of the spray chamber, with the rest contained therein. The total sprayed surface area in one run of the TS is 1.2 m2, and the operational zone for spray target placement is 0.7 m2, meaning that 58% of the applied volume deposits onto the targets. The TS can treat multiple surfaces (18 standard 15 × 15 cm tiles) in a single application, whereas the PT treats one surface at a time and a maximum area of around 0.0225 m2. An assessment of the time taken to perform spraying, including the setup, calibration and cleaning, showed that the cost of application using the TS was around 25–35 × less per tile sprayed. Standard operating procedures (SOPs) for calibration and use of both the Potter Tower and Track Sprayer have been developed.ConclusionsOverall, the TS represents a significant improvement over the PT in terms of the efficiency and accuracy of IRS formulation applications onto test substrates and offers a useful additional tool for researchers and manufacturers wanting to screen new active ingredients or evaluate the efficacy of IRS or other sprayable formulations for insect control.Graphical

A generic approach to estimate airborne concentrations of substances released by indoor spray processes using a deterministic 2-box model.

Sprays are used both in workplace and consumer settings. Although spraying has advantages, such as uniform distribution of substances on surfaces in a highly efficient manner, it is often associated with a high inhalation burden. For an adequate risk assessment, this exposure has to be reliably quantified. Exposure models of varying complexity are available, which are applicable to spray applications. However, a need for improvement has been identified. In this contribution, a simple 2-box approach is suggested for the assessment of the time-weighted averaged exposure concentration (TWA) using a minimum of input data. At the moment, the model is restricted to binary spray liquids composed of a non-volatile fraction and volatile solvents. The model output can be refined by introducing correction factors based on the classification and categorization of two key parameters, the droplet size class and the vapor pressure class of the solvent, or by using a data set of experimentally determined airborne release fractions related to the used spray equipment. A comparison of model results with measured data collected at real workplaces showed that this simple model based on readily available input parameters is very useful for screening purposes. The generic 2-box spray model without refinement overestimates the measurements of the considered scenarios in approximately 50% of the cases by more than a factor of 100. The generic 2-box model performs better for room spraying than for surface spraying, as the airborne fraction in the latter case is clearly overestimated. This conservatism of the prediction was significantly reduced when correction factors or experimentally determined airborne release fractions were used in addition to the generic input parameters. The resulting predictions still overestimate the exposure (ratio tool estimate to measured TWA > 10) or they are accurate (ratio 0.5-10). If the available information on boundary conditions (application type, equipment) does not justify the usage of airborne release fraction, room spraying should be used resulting in the highest exposure estimate. The model scope may be extended to (semi)volatile substances. However, acceptance may be compromised by the limited availability of measured data for this group of substances and thus may have limited potency to evaluate the model prediction.

A method for controlling and maintaining the thickness of a liquid layer during ultrasonic spraying

This work is described a method for indirectly controlling the height of the film of sprayed material on the oscillating surface of ultrasonic atomizer by changing the resonant frequency of the ultrasonic oscillator. The relevance of the development of this method is due to the need for the development and widespread use of the ultrasonic spraying method to solve the most pressing problems of modern industry. In this regard, there is a need to establish the dependences of the spraying performance on the height of the film of sprayed fluid on the oscillating plane of the atomizer and to create, based on the identified dependencies, a method for controlling and maintaining the necessary and sufficient height of the fluid film, the spraying of which will provide the best dispersion characteristics of the generated aerosol at a given spraying performance. As a result of the research, it was shown that in the operating range of film height of the sprayed fluid, the change in the resonant frequency can reach 100 Hz, which is sufficient to control the film height. This made it possible for the first time to develop a method for automatically controlling the ultrasonic spraying process, ensuring the maintenance of optimal modes of ultrasonic exposure (amplitude of vibrations of the spray surface) and the thickness of the sprayed fluid height.