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High Accuracy Meshfree Methods for Weakly Compressible Fluid and Associated Applications in Laser Induced Explosive Boiling
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Laser induced explosive boiling (LIEB) generated by localized high energy laser on solid surface has wide applications. Compared with traditional electric heating induced phase change process, LIEB has advantages in: (a) controllable ultra-short heating time, (b) no-pretreatment/fabrication required on substrate, (c) fully controllable heating size as well as heating energy. In this study, we utilized laser induced strong local heating by guiding laser into taped micro-nozzle to induce liquid ejection from the nozzle. The localized strong heating induces rapid phase change of ink liquid inside the nozzle. As a result, high pressure can be generated inside nozzle and can squeeze liquid out from the nozzle. This inkjet process has less limitation in ink materials than current inkjet techniques. By adjusting laser energy and laser pulse duration, we are able to generate different ink patterns vary from single droplet to ink spray consisted of sub-micron droplets. To better understand and control the LIEB process for construction laser inkjets, meshfree numerical analysis capable to study a LIEB process is also explored in this study. SPH was selected as the starting point of the meshfree numerical simulation considering its advantages in simulation of large distortion of free surface and moving interface of two phase flow. With a gaining experience in SPH, we noticed that it has limitations in achieving high enough numerical accuracy in derivative computing as well as providing stable numerical simulation without artificial smoothing processes. These limitations of traditional SPH prevent us from using SPH as a tool directly to study the LIEB. To solve the limitations of traditional SPH, we developed a new meshfree scheme providing following improvements: (a) using equation of state of fluid directly, which handles the P, ρ, T relation as well as the associated buoyancy forces without simplifications; (b) higher order accuracy in 1st and 2nd derivatives calculation providing 2nd and 1st order accuracy for random particle distribution and even higher accuracy for symmetric conditions. With this novel high order accuracy meshfree scheme developed in this study, we have a tool not only to stimulate the LIEB process but also bubble dynamics and micro cavitation directly.
Yang, Yu (2017). High Accuracy Meshfree Methods for Weakly Compressible Fluid and Associated Applications in Laser Induced Explosive Boiling. Doctoral dissertation, Texas A & M University. Available electronically from