An understanding of flow and dispersion in the human respiratory airways is necessary to assess the toxicological impact of inhaled particulate matter as well as to optimize the design of inhalable pharmaceutical aerosols and their delivery systems. Secondary flows affect dispersion in the lung by mixing solute in the lumen cross section. The goal of this study is to measure and interpret these secondary velocity fields using in vitro lung models. Particle image velocimetry experiments were conducted in a three-generational, anatomically accurate model of the conducting region of the lung. Inspiration and expiration flows were examined under steady and oscillatory flow conditions. Results illustrate secondary flow fields as a function of flow direction, Reynolds number, axial location with respect to the bifurcation junction, generation, branch, phase in the oscillatory cycle, and Womersley number. Critical Dean number for the formation of secondary vortices in the airways, as well as the strength and development length of secondary flow, is characterized. The normalized secondary velocity magnitude was similar on inspiration and expiration and did not vary appreciably with generation or branch. Oscillatory flow fields were not significantly different from corresponding steady flow fields up to a Womersley number of 1 and no instabilities related to shear were detected on flow reversal. These observations were qualitatively interpreted with respect to the simple streaming, augmented dispersion, and steady streaming convective dispersion mechanisms.

No abstract

Approved for public release; distribution is unlimited.ii REPORT DOCUMENTATION PAGE Form Approved OMB No. 0704-0188Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing the burden, to Department of Defense, Washington Headquarters Services, Directorate for Information Operations and Reports (0704-0188), 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number. PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS. REPORT DATE (DD-MM-YYYY)September 2008 ARL-TR-4611 SPONSOR/MONITOR'S ACRONYM(S) 9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES) SPONSOR/MONITOR'S REPORT NUMBER(S) DISTRIBUTION/AVAILABILITY STATEMENTApproved for public release; distribution is unlimited. SUPPLEMENTARY NOTES ABSTRACTSpin-stabilized artillery munitions were originally designed to provide precise ballistic fire on long-range targets. Today the challenge is to utilize these ballistic munitions in military operations in urban terrain environments where significantly higher levels of precision are required to minimize collateral damage. One strategy is to retrofit these munitions with some level of low-cost precision. Unique challenges arise when munitions designed to be ballistically precise are guided. Projectile flight is often stabilized by a high spin rate, which induces complex dynamics. Flight mechanics are further aggravated by adding a control mechanism. The goal of this study was to provide a fundamental understanding of various control mechanism strategies for spin-stabilized projectiles. Flight control systems were developed and executed in a six degree-of-freedom simulation. Formulating a generalized model of a control mechanism allowed investigation of parameters such as control force magnitude, control axial location, control lift-to-drag ratio, and control force duration. Results showed that control authority linearly related to control force magnitude. Maximal control authority was obtained by placing the control mechanism at the rear of the projectile. The variation with axial location was also determined since these results were valuable for instances when the control was unable to be located near the projectile base. A lower lift-to-drag ratio of the control mechanism decreased control authority and maximum range. Lastly, the trade-offs associated with continuous and pulsed flight control systems were quantified. Physical explanations for the simulation results were provided. SUBJECT TERMSflight dynamics, precise muni...

No abstract

High maneuverability of guided projectiles enables engagement of fleeing targets, opens the area of influence of a weapon system, and allows new missions to be performed such as prosecuting targets in defilade. Gun-launched precision munitions have unique constraints that create technical barriers to achieving enhanced maneuverability. Structural integrity during the gun launch event, packaging control surfaces within the launch tube, and affordability are paramount concerns. The present work is a fundamental investigation of the flight mechanics and guidance, navigation, and control technologies necessary to optimize maneuverability of affordable precision projectiles. Detailed aerodynamic modeling and nonlinear equations of motion for the flight of a fin-stabilized airframe meeting low control authority constraints were implemented in simulation. Flight control laws were developed for various maneuver schemes with different actuator realizations. Simulations were conducted over a large parameter space to evaluate maneuverability. Results provide the optimal parameters within the distinctive scope of gun-launched munitions. Flying a skid-to-turn airframe with four canards in the "X" configuration maximizes control authority with moderate volume allocation and actuator bandwidth requirements. Examination of dynamic stability along with static stability illustrates that high-fidelity aerodynamic characterizations are required when optimizing maneuverability due to the implications on the airframe design and flight control algorithm development. NomenclatureD = diameter S = reference area m = mass t a I I I , ,  = moment of inertia tensor, axial moment of inertia, transverse moment of inertia V = total velocity of projectile Q = dynamic pressure M = Mach number    , , = pitch, yaw, total angle-of-attack Z Y X , , = forces acting on projectile N M L , , = moments acting on projectile X C = axial force coefficient N C = normal force coefficient 0 l C = static roll moment coefficient p l C = roll damping coefficient m C = pitching moment coefficient q m C = pitch damping coefficient