Distributed Sensing of Unsteady Surface Pressure Fields
Navy SBIR 2019.2 - Topic N192-092
NAVSEA - Mr. Dean Putnam - email@example.com
Opens: May 31, 2019 - Closes: July 1, 2019 (8:00 PM ET)
TECHNOLOGY AREA(S): Battlespace, Electronics, Sensors
ACQUISITION PROGRAM: PMS 397 Technology Development, Signatures Task 3
OBJECTIVE: Develop a sensing and data acquisition system for exhaustive interrogation of the distributed, unsteady surface pressure field beneath turbulent boundary layers for complex hydrodynamic applications.
DESCRIPTION: All naval vehicles and structures that operate within a fluid flow are subject to turbulent flow conditions due to their high Reynolds numbers; accordingly, the design and analysis of turbulent boundary layer flow are of critical concern. Further, this turbulent boundary layer flow imparts a spatially and temporally unsteady pressure field on the flow surface, which can be a primary concern for acoustic and vibratory considerations.
Comprehensive measurements are made in a laboratory setting for simplified conditions; however, predictions and analysis of real configurations must rely on either limited data or broad assumptions. The measurement and analysis of the resulting unsteady pressure field have been continued topics of significant interest throughout the aerodynamic and hydrodynamic technical literature for several decades for a wide variety of conditions. Robust solutions for the constituent parts of the desired technology are available within the current commercial technology; however, the desired integrated system is not.
The needed R&D effort is therefore to design a sensing and data acquisition system that can provide the measurement characteristics of laboratory sensors (e.g., reliable calibrations, wide sampling frequency range, high channel counts). It needs to be robust and configurable in order to be applied in realistic marine environments and operate under water without restrictive handling or operational concerns. Components of both the sensing and acquisition aspects of this problem have been demonstrated in several instances. Data acquisition systems are abundant, and traditionally this type of pressure measurement is achieved through surface mounted microphones (electret or MEMs). There is difficulty however, in achieving compact systems with sufficient measurable dynamic range. The major R&D efforts that are foreseen are: 1) achieving a low-profile, minimally-invasive, reconfigurable measurement surface; 2) developing a probable innovation in sensing technology; and 3) implementing a robust acquisition system that requires limited user interaction.
An evaluation relative to a military standard is not envisioned, because this would constitute technology advancement, to which applying specific criteria is difficult. Further, different configurations and/or test articles would have varying needs based on flow conditions and specific orientations. However, the following are broad criteria in order to convey desired characteristics: 1) 100+ sensing elements within a 6x6 inch square footprint; 2) sensing and data acquisition capable of at least 10 kHz sampling with 80 dB of calibrated dynamic range; 3) operation in water at freestream flow conditions of up to 20 knots; 4) smooth, low-profile sensing “footprint” of less than 1 inch thickness; 5) robust sensing and data acquisition system capable of withstanding a sustained marine environment for a minimum of 24 hours with minimal alteration needed for insertion; and 6) sensing with limited user input and/or control necessary for data collection. Technology developed under this SBIR topic would provide a significant enhancement to current capabilities that support modeling and design of future Navy platforms, and would be applicable to a wide variety of programs.
PHASE I: Develop a concept for a potential system, approach, and/or solution as described in the Description. Demonstrate feasibility through modeling and simulation. Develop a Phase II plan. The Phase I Option, if exercised, will include the initial design specifications and capabilities description to build a prototype solution in Phase II.
PHASE II: Develop a prototype sensing and acquisition system per the requirements of the Phase I and Phase II Statement of Work (SOW) and to be utilized within a laboratory hydrodynamic setting (i.e., water tunnel). Consider continuous refinement and improvement to the prototype based on the outcome of testing. Determine performance evaluation based on the ability to achieve distributed pressure measurements with sufficient frequency and dynamic range resolution (as initially identified in the Description), maintain a percentage of functioning sensors greater than
75%, and insignificant effects due to prolonged operations in water. Address demonstration or identification of solution strategies for achieving operations with limited user control/input. Provide at least one functioning prototype for testing and delivery, plus back-up hardware for major components.
PHASE III DUAL USE APPLICATIONS: Tailor the measurement system to a specific (or multiple) large-scale configuration(s). Assist the Navy in transitioning the system onto several potential large-scale test articles.
The motivations for measuring and analyzing surface pressure fluctuations due to turbulent flow in complex configurations are broad. Accordingly, this topic has received considerable and varied attention within the technical literature for a variety of applications, including numerous acoustic and unsteady forcing concerns throughout the aerospace industry (at subsonic, transonic, and supersonic conditions), acoustic concerns in the automotive industry, and jet noise.
1. Blake, W. K. “Mechanics of Flow-Induced Sound and Vibration, Volume 2: Complex Flow-Structure Interactions.” Academic Press, Orlando, FL., 1986. https://www.sciencedirect.com/science/book/9780128092736
2. Catlett, M.R., Anderson, J.M., Forest, J.B., and Stewart, D.O. “Empirical Modeling of Pressure Spectra in Adverse Pressure Gradient Turbulent Boundary Layers.” AIAA Journal, Vol.54 (2), 2016. https://arc.aiaa.org/doi/10.2514/1.J054375
3. Lee, Y., Blake, W., and Farabee, T. “Modeling of Wall Pressure Fluctuations base on Time Mean Flow Field.” Journal of Fluids Engineering, Vol. 127, 2005, pp. 233-240. http://fluidsengineering.asmedigitalcollection.asme.org/article.aspx?articleid=1430130
4. Goody, M. “Empirical Spectral Model of Surface Pressure Fluctuations.” AIAA Journal, Vol. 42, No. 9, 2004, pp. 1788-1794. https://arc.aiaa.org/doi/pdf/10.2514/1.9433
5. Meyers, T. Forest, J., and Devenport, W. “The wall-pressure spectrum of high-Reynolds-number turbulent boundary-layer flows over rough surfaces.” Journal of Fluid Mechanics, Vol. 768, 2015, pp. 261-293. https://www.cambridge.org/core/journals/journal-of-fluid- mechanics/volume/A3328FD166C05A8EFB149B0D09BB8415
KEYWORDS: Turbulent Boundary Layer Flow; High Reynolds Number; Pressure Sensor Array; Unsteady Space- time Pressure Field; High Channel Count Arrays; Spectral Analysis