An Investigation of Vortex-based Hydropropulsors: Effect of Nozzle Contractility

PROPOSAL编号：CTS-0309672 PROPOSAL类型：调查员初始化PRINCIPAL调查员：Morteza GHARIBINSTITUTION：California Inst.涡流型水力推进器的研究：喷嘴收缩效应水母和人类心脏有什么共同之处？他们都使用一种简单但可靠的方法来泵送液体，这一过程是本研究计划的重点。最先进的实验流体力学技术，揭示这些抽水系统是如何由大自然设计的。这些进展将有助于检测这些生物系统的故障，有可能导致某些心脏病的早期诊断。此外，研究人员还创建了计算机算法，以快速“进化”自然产生的设计，用于具有特定性能要求的受生物启发的机器。脉冲喷射机制的相对简单和它在自然界中的明显成功表明，在人造系统中使用这些原则是认真考虑的。到目前为止，对这个问题的研究一直依赖于活塞从刚性圆柱形孔口喷射流体以产生涡环的实验和建模。由于壁面变形在其推进机制中的至高无上的重要性，单靠这一范例不足以理解生物相关情况下旋涡形成的支配过程。建议研究任意形状的收缩壁涡产生器的一般情况。试验将使用活塞-气缸布置，并采用改进的喷嘴，以便于孔口出口面积的时间变化。将询问由活塞速度和孔口出口面积组成的随时间变化的参数空间，以确定给定成本或适应函数(例如，最大推力、效率等)的最佳参数集。其目的是发现在可变面积脉冲喷气推进系统中控制推力产生的基本物理过程。通过这项技术，研究人员的目标是开发新的系统设计策略，范围从人造心脏瓣膜到先进的水下机器人概念。研究团队结合了加州理工大学航空学和生物工程系的资源。

ABSTRACTPROPOSAL NO.: CTS-0309672PROPOSAL TYPE: INVESTIGATOR INITIATEDPRINCIPAL INVESTIGATORS: MORTEZA GHARIBINSTITUTION: CALIFORNIA INST. OF TECH.AN INVESTIGATION OF VORTEX-BASED HYDROPROPULSORS: EFFECT OF NOZZLE CONTRACTILITYWhat do jellyfish and the human heart have in common? They both use a simple but reliable method to pump fluid, a process that is the focus of this research program. State-of-the-art experimental hydrodynamics techniques to uncover how these pumping systems are designed by Nature. Such advances will help in detecting malfunctions in these biological systems, potentially leading to earlier diagnosis of certain heart diseases. In addition, the researchers have created computer algorithms to rapidly "evolve" the naturally-occurring designs for use in biologically-inspired machines with specific performance requirements. The relative simplicity of the pulsed jet mechanism and its apparent success in nature suggests serious consideration of these principles for use in man-made systems. Studies of this question to date have relied on experimentation and modeling of a piston ejecting fluid from a rigid cylindrical orifice to generate vortex rings. This paradigm alone is insufficient for understanding the governing processes of vortex formation in biologically relevant cases, due to the paramount importance of wall deformation in their propulsive mechanisms. It is proposed to examine the general case of a wall-contracting vortex generator of arbitrary shape. Experiments will be conducted using a piston-cylinder arrangement with a modified nozzle designed to facilitate time-variation of the orifice exit area. A time-dependent parameter space consisting of piston velocities and orifice exit areas will be interrogated to determine an optimal parameter set for a given cost or fitness function (e.g. maximum thrust, efficiency, etc). The objective is to discover the fundamental physical processes governing thrust generation in variable-area pulsed jet propulsion systems. With this technology, the researchers are aiming to develop new strategies for designing systems ranging from artificial heart valves to advanced underwater vehicle concepts. The research team combines resources from the Aeronautics and Bioengineering departments at Caltech.