Wetted Surface Area Research Articles

Tuning the packed bed configuration for selective extraction of espresso non-volatiles based on polarity

The taste of espresso is impacted by the absolute and relative concentrations of numerous marker compounds extracted during the brewing process. Due to the complex diffusion-convection process, the resulting concentration of the compounds in the espresso cup is largely influenced by the extraction conditions. In our previous work (Vaca Guerra et al., 2023) we have demonstrated that the hydrodynamics of extraction is significantly impacted by the size distribution of the coffee particles. In the present work, using a similar approach, we evaluated its impact on the kinetics of the extraction of specific coffee marker compounds. The results obtained show that, even having similar extraction conditions, changes in the bed configuration, namely reducing the specific wetting surface area, decreased the extraction rate of the components asymptotically. Moreover, being polar components the most affected and non-polar the least, the impact of particle size was correlated with the polarity of the components, showing good agreement. This work provides insight into the possible ways to perform selective extraction from components with different polarities driven only by variations of the initial bed parameters and evaluating the necessary conditions to scale up the results to larger bed lengths.

Numerical Study on Resistance of Stepped Planing Hull

A stepped planing hull, also known as a step hull, is a hull modification that reduces the wetted surface area. Although this type of hull has proven effective in several ships, it is still rarely used. The step hull possesses numerous advantages that make it ideal for activities involving small and fast boats. However, regrettably, its full potential remains untapped at present. The purpose of this study was to identify the effect of variations in the angle of the step hull on resistance or drag. The study utilized the CFD method, and three hull configuration models were used at each change in hull step angle of 180º, 210º, 240º, and 270º. Configurations 1 and 2 have similarities in terms of rear hull length (600 mm), hull height (20 mm for configuration 1 and 30 mm for configuration 2), and deadrise angle (15° for configuration 1 and 20° for configuration 2). Configuration 3 has similarities with an 800 mm rear hull, 20 mm hull height, and 15° deadrise angle. It was found that as the Froude number increases, the coefficient of total resistance decreases. Conversely, as the Froude number increases, the resulting resistance also increases. The configuration with the highest resistance value corresponds to the alteration from configuration 2 with a hull step of 180°, and that the alteration from configuration 2 with a hull step of 270° corresponds to the configuration with the lowest resistance value. This study concludes that deadrise angle and the height of the step hull are the main factors that require careful consideration when designing ships that use a step hull. Therefore, this research provides an understanding of the step hull and can serve as a basis for the development of the step hull.

Comparison of Performance of Straight- and V-shaped Vanes Applied as Energy Saving Device to High-speed Boats

Hull Vane® is a device, generally utilizing a straight vane, installed horizontally near the stern of a vessel below the water surface and oriented in the transverse direction of the vessel with the purpose to save fuel consumption and to increase the vessel’s comfort. Because the bottom-hull form of a ship is generally curved, a non-straight vane may be more effective than a straight one when applied as Hull Vane®. The purpose of this study is to investigate the effectiveness of a V-shaped vane when applied as Hull Vane® on a 31 m high-speed crew boat. The study utilizes a computational fluid dynamics (CFD) method. CFD results show that the Hull Vane® decreased the bow-up trim of the boat, affected the boat’s wetted surface area, and decreased the height of the waves generated by the boat. The wave-height reduction due to the V-shaped Hull Vane® is larger than the straight Hull Vane®. Further, the Hull Vane® significantly reduced the total resistance of the boat at Froude number Fr = 0.34 with a larger reduction resulted from the V-shaped Hull Vane® (25.09% reduction for the straight vane and 30.75% reduction for the V-shaped vane). The observed resistance reduction decreased with increasing speed, ascribed to a too-large vane’s lift. The V-shaped Hull Vane® is more effective than the straight Hull Vane® in reducing the total resistance of the boat.

THEORETICAL BASICS OF MONITORING THE CONDITION OF THE ELECTRODES OF CHEMICAL CURRENT SOURCES BY THE METHOD OF ELECTROCHEMICAL IMPEDANCE SPECTROSCOPY

On the basis of the conducted critical review of modern physical models of the porous electrode, it сan be stated that under the conditions of non-uniform mass transfer taking into account the depth of the electrode, it is possible not only to develop new porous electrodes for a certain application, but also to control the state of electrochemical systems as a whole using the non-destructive method of electrochemical impedance spectroscopy. The presence of a macroscopic model of porous electrode allows one to use the integration of parameters over the surface of the electrode and obtain the average values of current, resistance and capacity within the electrode using the method of averaging in the volume ele­ment within the electrode, where porosity is the volume fraction of the void within the element, which is filled with electrolyte solution. This is the theoretical basis for using electrochemical impedance spectroscopy to assess the state of electrodes in electrochemical current sources. To take into account the influence of the aqueous electrolyte, it is possible to use a model taking into account the area of the effective wetted surface, which makes it possib­le to relate the wetting of the electrode pores with the electrolyte solution to the change in electrical conductivity and polarization of the electrode surface. In this case, when usingelectrochemical impedance spectroscopy, it is possible to obtain information about the following changes in primary current sources: 1– the effect of temperature, which leads to a decrease in the areas of the electrode wetted by the electrolyte, which affect the value of the capacity of the DEL, 2 – chemical processes that lead to the destruction of hydrophilic pores and pores with hydrophilic-hydrophobic walls, an increase in the hydrophobic component on the surface of the electrode, 3 – mechanical destruction of the electrodes. The use of models that take into account the geometry of pores makes it possible to obtain correct data for the analysis of the porous surface in the presence of an electrolyte and in cases of gas phase adsorption in presence of closed pores, as well as to use the value of the capacity on the surface of electrodes to assess the state of their performance.

Analysis of The Effect of Hull Vane Lifting Force on Fast Vessel Resistance: Straight Hull Vane

In previous studies by Saputra, the use of straight Hull Vane® increased ship's resistance. Based on hypothesis, this was caused by lifting force from Hull Vane® being too large, so that ship experienced bow trim. To reduce bow trim, smaller Hull Vane® was made including Hull Vane® with AR = 8.5, AR = 22.9 and AR = 28.94 with speeds which were 11 knots (Fn = 0.34), 17 knots (Fn = 0.53), 20 knots (Fn = 0.62) and 26 knots (Fn = 0.8). From simulation results, it was found that use of a straight Hull Vane® in every aspect ratio variation on vessel was only effective at 11 knots speed which could reduce ship's resistance up to 17%. For speeds above 11 knots, increased in aspect ratio can reduce resistance but resistance on ships with straight Hull Vane® was still greater than on ships without Hull Vane® because lift force by Hull Vane® at ship stern was still too large, so the bow of ship was more submerged than ship without Hull Vane®. This caused value of the wetted surface area (WSA) and value of hydrodynamic pressure more increased than ships without Hull Vane®, so value of ship's resistance also increased.

Design and modelling of porous gyroid heatsinks: Influences of cell size, porosity and material variation

Triply Periodic Minimal Surfaces (TPMS) are rapidly becoming favourable heatsink and heat exchanger topologies over traditional designs and other cellular structures. Their implicitly defined geometries provide increased heat transfer surface areas while maintaining smooth flow paths capable of further enhancement through flow tortuosity. Substantial investigations have been conducted on these structures within the field of thermal management systems, however more research is needed in understanding how design parameters effect flow and heat transfer performance. Cell size is a critical design parameter that sets the scale of these structures; however, little research has been conducted to date. This work attempts to investigate these gaps through a parametric and material study of TPMS gyroid sheets as heatsinks within turbulent flow. Samples of varying cell size and porosity are compared, where thermal and hydraulic performances are normalised against sample specific volume and wetted surface area. It is found that convective performance is agnostic to cell size, but greatly influenced by porosity. These reuslts are further compared against a reference fin heatsink. Performance measures such as thermal resistance (R), Nusselt number (Nu) and enhancement-to-losses (η) saw improvements of up to 53%, 300% and 42%, respectively when compared to the reference geometry. The results of this work may prove useful in further understanding the relationship between design parameters and heat transfer enhancement and help pave the way to meaningful performance optimisation for these structures.

Adaptive grid deformation method for CFD application to hull optimization

This work introduces a new grid deformation method for an efficient CFD-based optimization of ship hull forms. The method uses a two-level point transformation technique to manipulate grid points with a small number of design points. At the first level, generic B-spline is employed to transfer grid points based on movements of control points sampled inside a control box, ensuring accuracy and smoothness of surface modification. At the second level, Radial Basis Function with Wendland’s C2 continuity is adopted to interpolate movements of control points based on relatively few design points. It is shown to be effective in preserving good mesh quality and efficiency. The method is applied to the deformation of hull surfaces for ship models KVLCC2 and KCS, and to investigate the effects of bulbous bow on calm-water resistance with fixed Lpp. A regression model is proposed for ship length, location of buoyancy, wet surface area, and displacement. Numerical results show that the present method is well-suited for CFD-based hull form optimization with better efficiency.

Drag reduction and power optimization due to an innovative, toroidal hull form of an AUV

The use of unconventional design has become a norm for mission-specific underwater autonomous craft. Geometrical characteristics and drag optimized shapes of single-hulled underwater vehicles are known since 1970s and a few significant improvements have been possible since then. These are mostly related to the efficiency of a wake adapted propeller, positioned at the stern in wake of the hull. In a novel effort, when the propeller is integrated into the craft at center-line, and the hull in its entirety is designed to act as the duct, the drag of the hull is further reduced. This craft uses a toroidal hull form that distributes payload axi-symmetrically around an internal ducted thruster. The craft is designed to operate at an economic cruise speed of 2kn. The power consumption is optimized to achieve an endurance of over 500 miles through this implementation of a ducted thruster. The hydrodynamic characteristics of the new toroidal hull are compared to those of a reference design which is slender and conventionally shaped. This conventional design is intended for the same volume and dimensions of payload. A reduction of 13% in drag from the first to final design iteration is achieved. This reduction in drag is due to a higheer effective length to thickness ratio of the ducted AUV, quantified in terms of a new parameter defined as Ih . The reduction of the wetted surface area also contributes to the drag optimization. The article shows that the shape of the leading edge of the toroidal hull becomes important to achieve low drag. The process of design and optimization using CFD, with the most appropriate turbulence models is detailed. The beneficial effect of the acceleration induced in the flow at the leading edge and trailing edge of the hull by the integrated thruster is studied and explained with the help of CFD results.

Thermo-hydrodynamic characteristics and entropy generation in a tube heat exchanger using multiple head ribbed geometries

Heat exchangers are critical components in a wide range of industries, and optimizing their thermal performance remains an important research area. To augment the thermal efficiency in a heat exchanger, several investigations have been done to increase the wetted surface area using a rib profile. Still, there exists a lack of research attempts to change the geometrical shape, such as multiple-head ribbed geometry with coil revolution in a straight heat exchanger. Therefore, the present study takes a numerical approach to examine the effect of multiple ribbed geometries, considering the variable coil revolution of the rib profile in a straight-type heat exchanger. The study was initially validated from two experimental correlations and previous numerical work. Three rib surfaces (2 ribs, 3 ribs and 4 ribs) and three different coil revolutions (10 revolutions, 20 revolutions and 30 revolutions) were taken into consideration to make nine configurations. Air was used as fluid under heating conditions. The results have been represented in terms of velocity, temperature profiles, local Nusselt number (Nu), pressure drop, friction factors and entropy generations for all the configurations. A significant enhancement in heat transfer was found when the rib head number is lesser, whereas the coil revolution number is higher. Consequently, the highest Nusselt number (Nu) was observed in the configuration of 2 ribbed 30 revolutions, and the lowest was found in 4 ribbed 10 revolutions. Furthermore, the friction factor rises because of higher coil revolution for a specific rib head number. It is found that in four rib head geometry, the friction factor rises 2 times when the revolution number is 30 than the case of revolution number 10. It is also observed that the 4 rib head 10 revolution configurations provides the lowest entropy generations among the configurations. Thus, the study suggests choosing the right configuration to design a straight heat exchanger with ribbed head profile to get the highest thermal performance. Following this study, these design modifications can be applied to other types of heat exchangers as well.

Flux of the Wetted Surface Area on Ships’ Hulls in Major Ports of Korea

Biofouling is a significant means for introducing non-indigenous marine species internationally, which can alter habitats and disturb marine ecosystems. This study estimated the flux of ships’ wetted surface area (WSA) to Korea in 2020 to assess the risks of biological invasion via biofouling on ships’ hulls. The annual total WSA flux entering Korea was estimated to be 418.26 km2, with short-stay vessels (<3 weeks) contributing to 99.7% of the total WSA flux. Busan and Ulsan ports were identified as the main sources of high-risk flux, with container ships being a major vector in Busan and tankers in Ulsan. Gwangyang port had the third-highest total WSA flux, with nearly half of the flux driven from coastwise voyages, making it particularly vulnerable to the spread of hull fouling organisms. These findings could help enhance the management and inspection of hull fouling organisms in Korea.

Evaluation of Ti/Pt Anode Efficiency and Energy Consumption in Turbidity and Suspended Solids Removal from Paper Industry Wastewater: The Effect of pH and Support Electrolyte Type

In the research, different experimental setups were used to examine the treatment of wastewater from the paper industry using the electrooxidation method, one of the electrochemical treatment methods in the batch system. In the 2000 mL volume jacketed glass reactor utilized for the treatment of wastewater from the paper industry, 4 anode and 4 cathode sieve type plates of 7 cm x 10 cm dimensions were positioned at 0.5 cm intervals, and 1200 mL wastewater was used in the tests. Coated sieve type Ti/Pt electrodes were employed as the anode in the electrooxidation studies, and uncoated sieve type Ti electrodes were used as the cathode. It was determined that the active anodic wet surface area was 1078 cm2 . The removal rates of pollutant parameters such as turbidity and SS (Suspended Solids) in the experiments; the effects of wastewater initial pH value and supporting electrolyte type parameters were investigated. According to the results, the most effective pH value for Ti/Pt anode type at 400 rpm mixing speed was determined to be waste water natural pH (7.5), and 0.50 M NaCl was the most successful supporting electrolyte type. 96.92% Suspended Solids removal efficiency and 95.38% turbidity removal efficiency for Ti/Pt anode were achieved under ideal conditions. In addition, 312.05 kW-hour/kg COD is determined as the energy consumption value.

A parametric design approach for multi-lobed hybrid airships

AbstractIn recent years, there has been an increasing interest in the research and development of hybrid airships for various applications. Airship design involves multiple design parameters from various disciplines that interact mutually. Existing design methodologies, however, are often limited to fixed shapes and geometry. This paper provides a comprehensive parametric design approach for the sizing of multi-lobed hybrid air vehicles for low- and high-altitude applications. The proposed design techniques are robust so that the designer has the freedom to change the number of lobes, the relative location of lobes, the envelope profile, and the optimiser for the design optimisation process. The outcomes of the proposed methodology are envelope volume, wetted surface area, length and span of the envelope, sizing and layout of the solar array, and sizing and layout of the fins. The modeling techniques highlighted in this paper are very efficient for the design and optimisation of multi-lobed airships in the conceptual design phase with a large design exploration space. The robustness of the shape generation algorithms is tested on some of the standard envelope profiles of airships. The effect of the shape and geometry of the multi-lobed envelope on added mass is demonstrated through the added mass estimation using Boundary Element Method.

Hydrodynamic investigations of a cross-domain vehicle with the capability of high-speed cruising on water surface

With the growing demands for marine resource exploitation and marine defense security deployment, unmanned surface vehicles (USVs) and autonomous underwater vehicles (AUVs) are of great value in both civil and military fields. However, both USVs and AUVs can only operate in a single scenario, which is difficult for complex cross-domain missions. Here, we propose a cross-domain vehicle (CDV) with both high-speed mode as USV and diving mode as AUV. To obtain the capability of high-speed cruising on the water surface, two sets of well-tailored hydrofoils are employed for drag reduction by adjusting the attitudes of CDV. Numerical investigations are carried out to evaluate the hydrodynamic characteristics of the CDV at different velocities. Moreover, prototype tests are conducted in open water, demonstrating its technical feasibility and validating the numerical methods. The results demonstrate a maximum drag reduction of 43% and a significant improvement in longitudinal stability with elaborate design of the hydrofoils. The mechanism of the drag reduction is revealed by flow field analysis, which is a joint effect resulting from the inhibition of wave-making as well as the reduction of the wetted surface area. The current work has significant value for future improvement of CDVs.

INVESTIGATING THE COMPARISON OF SHIP RESISTANCE COMPONENTS BETWEEN U AND V-SHAPED HULLS

The selection of a hull design with minimal drag is an important effort to reduce emission levels on ships. Two different hull shapes, U and V hulls, have unique properties that affect their drag production, which has been studied extensively in the past. This study aims to re-examine the differences between the two hull types by conducting a simple analysis of drag prediction results using empirical and numerical slender body methods. Both hull models in this study have the same size and volume. The results indicate that the U hull has a higher frictional resistance ( ) than the V hull due to its wider wetted surface area ( ). Additionally, the viscous pressure resistance ( ) and form factor coefficient ( ) of the U hull are also higher than those of the V hull. However, for Froude numbers (Fr) above 0.245, the U hull has lower wave resistance ( ) than the V hull, whereas for Fr below 0.245, the U hull has higher . Overall, the U hull produces a higher total resistance ( ) than the V hull at low speeds, but a lower at high speeds. Therefore, the choice of hull shape for minimizing a ship's resistance is influenced by the desired speed of service. If Fr is low, below 0.24, a V-shaped hull is more suitable. However, if Fr is higher than 0.24, a U-shaped hull is more appropriate.

Experimental investigation of surface wettability induced runback water flow and heat transfer behavior

Aircraft icing is a serious threat to flight safety, therefore, active anti-icing systems are widely utilized in the aviation industry. In order to reduce the energy consumption of anti-icing systems, passive anti-icing methods combined with superhydrophobic surfaces are of interest. However, the passive protection of superhydrophobic surfaces is not as effective as expected when applied to aircraft anti-icing, which involves high speed and high humidity condition. The flow and heat transfer of runback water is an issue of fundamental importance for understanding of the aircraft anti-icing processes. In order to understand the mechanism of passive anti-icing on superhydrophobic surface, this study experimentally investigated the runback water flow and heat transfer behavior on airfoil with different surface wettabilities in a straight-flow spray wind tunnel. It was found that the runback water film was more likely to break up and form the rivulets when the wettability is more hydrophobic, with the breakup location closing to the leading edge, and the wetted surface area became smaller, therefore reducing ice accumulation. The water droplets on superhydrophobic surface shed away easily to make the surface have no runback water, which enables low energy consumption for the dry anti-icing method. The coupled analysis of the flow and heat transfer behavior indicated that surface wettability altered the runback water patterns, leading to changes in the convective heat transfer coefficient and heat transfer area, ultimately affecting the overall heat transfer process. In addition, the droplet erosion resistance of superhydrophobic surfaces prepared by two methods were tested and compared in this study.

A Statistical Analysis for Optimisation of a Hybrid BBDB-PA in Mantanani Island, Sabah

The hybrid form of wave energy converter (WEC) is a recent advancement in research concerning harvesting energy from the ocean. This study investigates the effect of size and position of the point absorber integrated with a backward bent duct buoy. The aim of this optimisation is to maximise the WEC-absorbed power and heave response amplitude operators (RAO) at a specific sea site. The optimisation process was applied based on the data collected over a one-year period about sea characteristics for a nearshore region of the Mantanani Island. We present a methodology for optimising the Hybrid BBDB-PA based on a statistical analysis and the hydrodynamics of the system in the frequency and time domain. We used the ANSYS/AQWA software for the hydrodynamic diffraction analysis, and the design of experiments method was applied through the statistical software to determine the optimised parameters. We found that the diameter and gap length between PA and BBDB were found to significantly influence two characteristics, namely, heave RAO and maximum power absorption of PA. This observation shows that the PA size was directly proportional to the performance because a higher diameter has more contact with the ocean’s wet surface area with the ocean and absorbed higher wave energy. Moreover, the gap length between the PA and BBDB was directly correlated with a wavelength, which followed the theoretical value for peak-to-trough length, where the maximum wave height occurs. Despite the condition parameter, we discovered that the WEC position and arrangement were responsible for the highest value of the power, regardless of the PA position used in the experiment. The results of this research provide recommendations for optimising the ocean energy harvesting in order to fully utilise ocean space for energy.

Fabrication and characterization of Orlistat Liquisolid tablets

The aim of the work was to improve the dissolution properties of the practically insoluble anti-obesity drug, Orlistat by utilizing liquisolid technique. Different liquisolid tablets were prepared by dissolving Orlistat in PG with Avicel PH 102 as carrier, Aerosol 200 as coating material and Sodium starch glycolate as disintegrating agent. Additives such as PVP, HPMC and HPG were incorporated into the formulations to improve dissolution characteristics. The formulated liquisolid tablets were evaluated for post compression parameters such as weight variation, hardness, friability, drug content and in-vitro dissolution studies. FT-IR study suggested that there was no chemical interaction between the drug and excipients. DSC was performed to evaluate the physicochemical properties of the liquisolid tablets, which confirm the conversion of crystalline form of the drug to the amorphous form in liquisolid tablets. The result showed that liquisolid formulation of Orlistat exhibited higher percentage of drug release than directly compressed tablets which show significant benefit of liquisolid tablet in increasing wetting properties and surface area of drug available for dissolution.

Using low-field NMR relaxation to optimise particulate dispersions

Formulation of particulate dispersions is a difficult industrial problem, with a multitude of system details influencing the final outcome. Solvent relaxation NMR is shown to help optimise the formulation of particulate dispersions of a range of widely used commercial silicas. Solvent at the particle interface is sensitive to details of the formulation, and it is shown that the average solvent spin-relaxation time in a dispersion can be used to monitor wetted surface area, sample sedimentation, and additive amounts; chemical syntheses and mechanical degradation of silicas are also monitored to optimise the dispersions. The experiments, which can be carried out on bench-top or on-line spectrometers, are not limited to silicas and can be generalised to other particles in a range of aqueous and non-aqueous dispersions, providing useful feedback to the formulator anywhere surfactants, polymers, pH, ionic strength, Hamaker constants, and surface charge play a role in stabilisation. • Rapid NMR relaxation measurements reveal variation in silica surface chemistry. • Breakup of silica aggregates is monitored by NMR relaxation to optimise processing. • NMR relaxation measurements provide facile quality control tests for hydrogels. • Silica particle syntheses are monitored by NMR relaxation.

Numerical study on a hybrid WEC of the Backward Bent Duct Buoy and Point Absorber

This study aims to investigate a wave energy converter that utilizes heave motion as the primary driver for energy harvesting. The main objective is to examine the effect of applying a new form of hybrid Backward Bent Duct Buoy (BBDB) with Point Absorber (PA) at various wave conditions. The effects of single BBDB, PA, and a new hybrid form of BBDB-PA on heave Response Amplitude Operator (RAO) and power absorption were examined within various ranges of wave periods under regular wave conditions using ANSYS-AQWA. The results reveal that the characteristics of excitation force, radiation damping coefficient, and added mass of the BBDB and PA are significantly influenced by the new hybrid form. This observation is due to the advantage of the hybrid form that would have more contact with the wet surface area. Moreover, the hybrid BBDB-PA yields higher heave RAO and power absorption compared to the non-hybrid counterpart. The results offer recommendations for optimizing the design of hybrid WECs and imply the possibility of synergy between BBDB and PA to fully utilize ocean space for energy.

Comparative Analysis of Slamming Phenomenon Prediction between U and V Hulls using Strip Theory Method

Choosing the right hull shape is important in designing a ship, for example, a U-section or V-section of the hull. The hull shape will affect various aspects, such as design, resistance, seakeeping, structure and production. The ship hull must be properly designed so that it can operate according to the ship’s mission. From the seakeeping aspect of the ship's motion at sea, the difference in the hull shape will result in different motions and dynamic effects such as the slamming phenomenon. Based on the difference in the hull shape cases, this study analyzed the difference in the probability of slamming between the U and V hulls. Both hulls were made based on Formdata and almost all parameters were made the same. Parameters that cannot be forced to be the same are WSA (wetted surface area), (coefficient of waterplane area), and (distance of keel to buoyancy), where those parameters determine the difference in the results. The calculation of RAO (operator amplitude response) was obtained using the strip theory method which assisted by Maxsurf Motion software. The results became the input for the calculation of the slamming probability. The study results show that the U hull has a higher probability of slamming occurrence than that of the V hull, with the difference in values ranging from 20% to 35%. Therefore, the U hull will get more frequent slamming loads, so it has the potential to have a higher structural failure (fatigue) than that of the V hull.