Transonic airfoil analysis and design in nonuniform flow

A nonuniform transonic airfoil code is developed for applications in analysis, inverse design and direct optimization involving an airfoil immersed in propfan slipstream. Problems concerning the numerical stability, convergence, divergence and solution oscillations are discussed. The code is validated by comparing with some known results in incompressible flow. A parametric investigation indicates that the airfoil lift-drag ratio can be increased by decreasing the thickness ratio. A better performance can be achieved if the airfoil is located below the slipstream center. Airfoil characteristics designed by the inverse method and a direct optimization are compared. The airfoil designed with the method of direct optimization exhibits better characteristics and achieves a gain of 22 percent in lift-drag ratio with a reduction of 4 percent in thickness

Calculation of vortex lift effect for cambered wings by the suction analogy

An improved version of Woodward's chord plane aerodynamic panel method for subsonic and supersonic flow is developed for cambered wings exhibiting edge separated vortex flow, including those with leading edge vortex flaps. The exact relation between leading edge thrust and suction force in potential flow is derived. Instead of assuming the rotated suction force to be normal to wing surface at the leading edge, new orientation for the rotated suction force is determined through consideration of the momentum principle. The supersonic suction analogy method is improved by using an effective angle of attack defined through a semi-empirical method. Comparisons of predicted results with available data in subsonic and supersonic flow are presented

Theoretical aerodynamics of upper-surface-blowing jet-wing interaction

A linear, inviscid subsonic compressible flow theory is formulated to treat the aerodynamic interaction between the wing and an inviscid upper-surface-blowing (USB) thick jet with Mach number nonuniformity. The predicted results show reasonably good agreement with some available lift and induced-drag data. It was also shown that the thin-jet-flap theory is inadequate for the USB configurations with thick jet. Additional theoretical results show that the lift and induced drag were reduced by increasing jet temperature and increased by increasing jet Mach number. Reducing jet aspect ratio, while holding jet area constant, caused reductions in lift, induced drag, and pitching moment at a given angle of attack but with a minimal change in the curve of lift coefficient against induced-drag coefficient. The jet-deflection effect was shown to be beneficial to cruise performance. The aerodynamic center was shifted forward by adding power or jet-deflection angle. Moving the jet away from the wing surface resulted in rapid changes in lift and induced drag. Reducing the wing span of a rectangular wing by half decreased the jet-circulation lift by only 24 percent at a thrust coefficient of 2

Theoretical predictions of jet interaction effects for USB and OWB configurations

A wing jet interaction theory is presented for predicting the aerodynamic characteristics of upper surface blowing and over wing blowing configurations. For the latter configurations, a new jet entrainment theory is developed. Comparison of predicted results with some available data showed good agreement. Some applications of the theory are also presented

VORCAM: A computer program for calculating vortex lift effect of cambered wings by the suction analogy

A user's guide to an improved version of Woodward's chord plane aerodynamic panel computer code is presumed. The guide can be applied to cambered wings exhibiting edge separated flow, including those with leading edge vortex flow at subsonic and supersonic speeds. New orientations for the rotated suction force are employed based on the momentum principal. The supersonic suction analogy method is improved by using an effective angle of attack defined through a semiempirical method

TRANDESNF: A computer program for transonic airfoil design and analysis in nonuniform flow

The use of a transonic airfoil code for analysis, inverse design, and direct optimization of an airfoil immersed in propfan slipstream is described. A summary of the theoretical method, program capabilities, input format, output variables, and program execution are described. Input data of sample test cases and the corresponding output are given

A New Framework for Evaluating Commodity Promotion Programs: What Can We Learn from Disaggregate Data?

Marketing,

Countercyclical Price Movements during Periods of Peak Demand: Evidence from Grocery Retail Price for Avocados

Using a unique micro dataset and advanced panel models, this study examines the effects of demand shocks on grocery retail price for avocados, a key Californian fresh produce commodity. Retail prices for avocados exhibited countercyclical movements over seasonal demand shocks for avocados associated with some holidays and events. Demand for avocados is shown to be higher during some holidays/events, e.g., Christmas/New Year, Super Bowl Sunday, and Cinco de Mayo. Super Bowl Sunday and Cinco de Mayo are identified as holidays/events associated with idiosyncratic demand peaks for avocados, but not associated with high aggregate consumer demand. Retail price and margin were significantly lower during some holidays/events associated with high demand for avocados, e.g., Christmas/New Year, Super Bowl Sunday, and Cinco de Mayo. The study also shows that the increase in demand and decrease in retail price during holidays/events with demand peaks for avocados was present for both large and small sizes of avocados, and the size of demand increases and the size of price reductions were not statistically different between large and small size of avocados. Furthermore, shipping price did not change or increased slightly, and hence moved opposite from retail the price during most holidays/events with high demand for avocados. We examine and test the predictions by four classes of theories that put forward to explaining countercyclical price movements over demand peaks. Overall, the evidence provides support for the Lal and Matutes (1994) model that retailers reduce retail prices and/or margins during a commodity's high-demand periods, but does not support alternative explanations for countercyclical price movements, such as Bernheim and Whinston (1990), Warner and Barskey (1995), or Nevo and Hatzitaskos (2006). The findings are consistent with the findings by Chevalier, Kashyap, and Rossi (2003). The study estimates the effects of the CAC's promotion programs on retail sales, retail price, and shipping price at disaggregate level. The analysis demonstrates that the CAC's promotion programs were associated with positive retail sales. In particular, the evidence from the long-panel data suggests that the CAC's promotion programs were successful in raising avocado sales. There is no evidence that retailers charged higher prices during the CAC's promotions.retail price, retail price determination, countercyclical price movement, dynamic panel model, GMM, Demand and Price Analysis,

Impact of Sequential and Partial Trade Liberalization for Mexican Hass Avocado Imports to the U.S. during 1998-2004

International Relations/Trade,

Grocery Retailer Pricing Behavior for California Avocados with Implications for Industry Promotion Strategies

Rising concentration and consolidation of sales among large supermarket chains in the U.S. and other countries, due in part to a recent wave of mergers in food retailing, have made retailers' role in the food industry a topical issue. Using a unique micro dataset, this paper investigates retailer pricing issues for avocados, a key California specialty commodity, and analyzes the implications of retailer pricing behavior for the effectiveness of avocado industry advertising programs. The methodologies developed and the results achieved in this study should have broad applications across the produce sector, the food industry, and the grocery retail market. We find that retail prices for avocados are highly dispersed both spatially and temporarily. The analysis also illustrates the existence of a "regular" retail price for avocados. Downward deviations from the "regular" price dominated changes in retail prices, in particular, temporary price reductions accounted for 27 percent of retail price variations. The study examines the effects of fundamental cost and demand factors on determination of retail prices. We conclude that costs are not a primary factor in setting retail prices for avocados. Retailers' sales strategies, which reflect decreases in retail margins rather than decreases in costs, explained much of the observed temporary price reductions for avocados. Retail prices for avocados also exhibited countercyclical movements over seasonal demand cycles. The findings provide support for Lal and Matutes' (1994) hypothesis that retailers reduce prices or margins during a product's high-demand periods. We investigate how retailers respond to industry promotions and, in turn, how retailer response enhances or vitiates the effectiveness of industry promotions. The approach of "Difference-in-Difference" is employed to evaluate the effects of the California Avocado Commission's (CAC) promotion programs on retail pricing and sales. The analysis demonstrates that the radio campaign and outdoor advertisements were successful in raising avocado sales. There is no evidence that retailers charged higher prices during the CAC's promotions. Nonetheless, the CAC's promotion programs could be enhanced if retailers were better informed about the advertising campaigns. Other noteworthy results include the fact that retail margins increased significantly as shipment volumes increased, indicating the presence of retailer oligopsony power. Also notable was the rather strong evidence that retail prices were significantly lower as a function of the amount of avocados imported from Chile and Mexico, meaning that consumers have benefited from trade liberalization for avocados.F13, L1, L81, Q1, Q13, Demand and Price Analysis, Marketing,