Use Of High-pressure Water Jets Research Articles

Farmer perception, knowledge and management of the scale insect pest complex infesting crops and trees in Coastal Kenya

Scale insects and mealybugs (Hemiptera: Sternorrhyncha: Coccomorpha) are serious plant sap-sucking pests affecting a wide range of cultivated crops and tree species. The insects are highly diverse and can have devastating effects on yields due to lack of farmer awareness and inappropriate management practices. Recent alien mealybug invasions in Kenya include among others, papaya mealybug (Paracoccus marginatus), a highly invasive pest that is spreading quickly. Farmer experience with diverse crop pests can support development of a successful pest management strategy and contribute to reduced impacts on both crop yields and agro-biodiversity. This socio-economic survey was carried out in three coastal counties of Kenya (Mombasa, Kilifi and Kwale) to establish the impact of scale insect and mealybug pests on farmer livelihoods and to document the perception, knowledge and management practices used by smallholder farmers. Data from oral interviews using ODK were administered to respondents and analysed using Excel and GENSTAT. It emerged that 26% of the respondents were familiar with scale insects and 51% with mealybugs, respectively. Of these, 78.13 % and 94% acknowledged having encountered scale insects and mealybugs, respectively, on their farms. The farmers confirmed that scale insect pests affected a high diversity of crops and trees. About 56% of the respondents used pesticides to control the pests while 25% did not apply any management strategy. The remaining 19% practiced cultural control methods such as field sanitation and intercropping with less susceptible crops. Pesticides were reported to be moderately effective (41-70%) at controlling scale insects and mealybugs. Other management options reported by farmers included farm hygiene, the use of high-pressure water jets, and applications of ash and bio-pesticides such as home-made neem extract. Based on the findings, it is recommended that capacity building for farmers and input providers be undertaken to enhance the knowledge of scale insect and mealybug pest biology, symptoms of crop and tree attack, host ranges and management practices. Additonally, training on the use of low-risk pest control products and innovative control methods should be undertaken to reduce the impact of the pest on crop production and agro-biodiversity. Keywords: Farmer knowledge, management, mealybugs, scale insects and socio-economic survey.

Numerical simulation of the abrasive waterjet (awj) machining: multi-fluid solver validation and material removal model presentation

The increasing use of high-pressure water jets in the industry for machining materials yields numerous studies aiming at the optimization of this technology. Since the experimental study of pure or abrasive water jet cutting is complex to carry out, the numerical simulation of this process stands as an attractive alternative. Such a simulation relies on the coupling of numerical tools devoted on one hand to the description of the high-velocity jet and on the other hand to the deformation of the impacted material. The present paper provides a careful validation for the simulation of an impinging abrasive liquid jet, taking progressively into account the necessary features: impingement, free-surface, particles.

Application of high-pressure waterjets for comminution

The interaction of high-pressure waterjets with fluids and solids is characterized by the possibility to apply determined stresses with a defined quantity of energy. Beside its classical application in the material and surface processing, the high-pressure waterjet technique found entry into the comminution technique, particularly in connection with new tasks in the environmental and recycling industry. In this contribution, fundamentals and mechanisms of high-pressure waterjets as well as their interactions with solids will be presented. Examples of the use of high-pressure waterjets for comminution are given.

An expert process planning system for meat cutting by high pressure water-jet

Abstract The use of high-pressure water-jets as a cutting tool has recently been increasing. Most applications have been directed at harder materials, and at those that are more difficult to cut by established methods. For the former, abrasive is used; for relatively soft materials, such as food, paper, foam, and linoleum, solely water is used, these materials usually being shaped to a specified profile. An expert process planning system for water-jet cutting (WJC) of soft materials, particularly animal carcasses, is described. A procedure for material selection of the end-product, that is meat, such as pork, beef, lamb and chicken, is explained. Various operations within the water-jet cutting process in relation to these specified meat end-products are investigated. Finally, the cutting process variables, such as water-jet pressure, traverse speed, the diameter of the nozzle and its stand-off distance from the animal carcass, are identified. These findings are then related to experiments on WJC of beef, chicken, lamb and pork. These tests revealed that WJC may be successfully applied to beef and pig meat, although further trials are necessary to explore the potential advantages of this technique to industry, especially for cutting through bone. (It might be noted that these meats are harder than chicken. When the latter underwent WJC, both the meat and its bone were readily cut). The process planning system so developed has considerable relevance to automation in meat cutting industry, especially in relation to productivity, total cost through elimination of labour-related costs, and the attractions of WJC as a hygienic method of processing of food products.

An expert process planning system for meat cutting by high pressure water-jet

The use of high-pressure water-jets as a cutting tool has recently been increasing. Most applications have been directed at harder materials, and at those that are more difficult to cut by established methods. For the former, abrasive is used; for relatively soft materials, such as food, paper, foam, and linoleum, solely water is used, these materials usually being shaped to a specified profile. An expert process planning system for water-jet cutting (WJC) of soft materials, particularly animal carcasses, is described. A procedure for material selection of the end-product, that is meat, such as pork, beef, lamb and chicken, is explained. Various operations within the water-jet cutting process in relation to these specified meat end-products are investigated. Finally, the cutting process variables, such as water-jet pressure, traverse speed, the diameter of the nozzle and its stand-off distance from the animal carcass, are identified. These findings are then related to experiments on WJC of beef, chicken, lamb and pork. These tests revealed that WJC may be successfully applied to beef and pig meat, although further trials are necessary to explore the potential advantages of this technique to industry, especially for cutting through bone. (It might be noted that these meats are harder than chicken. When the latter underwent WJC, both the meat and its bone were readily cut). The process planning system so developed has considerable relevance to automation in meat cutting industry, especially in relation to productivity, total cost through elimination of labour-related costs, and the attractions of WJC as a hygienic method of processing of food products.

High pressure waterjet cooling/lubrication to improve machining efficiency in milling

The efficiency of the metal cutting operations depends upon the thermal/frictional conditions at the tool-chip interface. The use of high pressure waterjet as a coolant/lubricant to improve the thermal/frictional conditions in milling operations was studied here. The influence of high pressure waterjet delivered into tool-chip interface in two different methods, namely, waterjet injected directly into the tool-chip interface through a hole in the tool rake face, and waterjet injected into tool-chip interface through an external nozzle, was explored in this study. The effectiveness of these developed methods was evaluated in terms of cutting force, surface finish, chip shape and tool wear.

High pressure waterjets for oil containment in calm and wavy waters; a parametric study

The use of high pressure waterjets (HPWJ) as oil barriers has been proposed and tesed. It has been shown that a series of waterjets directed horizontally above the free water surface provide an effective means of containing or deflecting oil slicks. The waterjets generate a high speed air flow capable of moving the surface layer of the liquid. A numerical model is implemented to study the chracteristics of the entrained turbulent air flow using the Spectral Element Method (SEM) and an algebraic turbulent model for the Reynolds stresses. A test of the code is done for turbulent Couette Flow to check the accuracy of the calculated shear stresses against published data. A parametric study is performed to evaluate the HPWJ system performance at various operating and design parameters which include manifold pressure, nozzle flow rate, nozzle characteristics, jet height and surface wave conditions. The total driving shear force and power required for effective containment are used as performance measures. Shear stress and the total driving shear force at the air-liquid interface are calculated over a reference waterjet distance. Performance is measured under calm and wavy sea conditions. It is found that the containment pressure required to generate a given shear force in wavy surface conditions are 30–50% less than those required in calm water. The driving shear force decreases as the jet height above the liquid surface increased. Shear forces also appear to decrease with the reduction of the entrained air flow. The latter is governed by nozzle type, spread angle and spacing. The results of the parametric study are consistent with the trends observed experimentally, and could be used in optimising the system design and performance as well as in setting appropriate operational conditions.

A study of rock erosion using high-pressure water jets

This study is directed towards developing a better understanding of the erosion mechanisms involved in the use of high-pressure water jets for cutting in rock materials. Theories to explain the cutting action of high-pressure water jets have been proposed by Crow [1,2] ( Int. J. Rock Mech. Min. Sci. & Geomech. Abstr. 10, 567–584, 1973 and 12, 203–212, 1975) and Rehbinder [3] ( Rock Mech. 12, 247–257, 1980). These theories predict the depth of kerf cut by the jet in terms of the rock and fluid properties and the water jet system parameters. While both theories produce reasonable results for certain cases, neither is completely satisfying. For pedagogical purposes this paper is organized in sections. Following the Introduction, a review is given of published empirical findings from studies of rock erosion using high-pressure water jets. Then the theories of Crow and Rehbinder are compared with published experimental results to determine how well these two models predict the kerf depth in rock cut by a water jet. Next, results are given of new water jet rock kerfing experiments conducted using a factorial approach in the experimental design. Empirical models fitted to these results identify the relative importance of both the rock properties and the water jet parameters in the erosion process. There follows a description of a new laboratory technique employed to examine micro-structural rock damage caused by the water jet in eroding the rock. The objective of all of this work is to gain new insight into the mechanisms of rocl erosion. The concluding section then outlines a proposed new physical model for rock erosion by a high-pressure water jet.

Use of high-pressure water jets in mining operations (In French)

Use of high-pressure water jets in mining operations (In French)

Use of high-pressure water jets in construction

Use of high-pressure water jets in construction