Investigation of oscillating cascade aerodynamics by an experimental influence coefficient technique

Fundamental experiments are performed in the NASA Lewis Transonic Oscillating Cascade Facility to investigate the torsion mode unsteady aerodynamics of a biconvex airfoil cascade at realistic values of the reduced frequency for all interblade phase angles at a specified mean flow condition. In particular, an unsteady aerodynamic influence coefficient technique is developed and utilized in which only one airfoil in the cascade is oscillated at a time and the resulting airfoil surface unsteady pressure distribution measured on one dynamically instrumented airfoil. The unsteady aerodynamics of an equivalent cascade with all airfoils oscillating at a specified interblade phase angle are then determined through a vector summation of these data. These influence coefficient determined oscillation cascade data are correlated with data obtained in this cascade with all airfoils oscillating at several interblade phase angle values. The influence coefficients are then utilized to determine the unsteady aerodynamics of the cascade for all interblade phase angles, with these unique data subsequently correlated with predictions from a linearized unsteady cascade model

Wind tunnel wall effects in a linear oscillating cascade

Experiments in a linear oscillating cascade reveal that the wind tunnel walls enclosing the airfoils have, in some cases, a detrimental effect on the oscillating cascade aerodynamics. In a subsonic flow field, biconvex airfoils are driven simultaneously in harmonic, torsion-mode oscillations for a range of interblade phase angle values. It is found that the cascade dynamic periodicity - the airfoil to airfoil variation in unsteady surface pressure - is good for some values of interblade phase angle but poor for others. Correlation of the unsteady pressure data with oscillating flat plate cascade predictions is generally good for conditions where the periodicity is good and poor where the periodicity is poor. Calculations based upon linearized unsteady aerodynamic theory indicate that pressure waves reflected from the wind tunnel walls are responsible for the cases where there is poor periodicity and poor correlation with the predictions

Experimental investigation of transonic oscillating cascade aerodynamics

Fundamental experiments are performed in the NASA Lewis Transonic Oscillating Cascade Facility to investigate the subsonic and transonic aerodynamics of cascaded airfoils executing torsion mode oscillations at realistic values of reduced frequency. In particular, an unsteady aerodynamic influence coefficient technique is developed and utilized. In this technique, only one airfoil in the cascade is oscillated at a time, with the resulting airfoil surface unsteady pressure distribution measured on one dynamically instrumented reference airfoil. The unsteady aerodynamics of an equivalent cascade with all airfoils oscillating at any specified interblade phase angle are then determined through a vector summation of these data. These influence coefficient determined oscillating cascade data were correlated with: (1) data obtained in this cascade with all airfoils oscillating at several interblade phase angle values; and (2) predictions from a classical linearized unsteady cascade model

Figuration & Frequency: A Usage-Based Approach to Metaphor

Two of the major claims of the cognitivist approach to metaphor, the paradigm which has emerged as dominant over the last three decades, are 1) that metaphor is a conceptual, rather than strictly linguistic, phenomenon, and 2) that metaphor exemplifies processes which are at work in cognition more generally. This view of metaphor is here placed within the context of the functionalist approach to language, which asserts that linguistic structure is emergent in nature, the use of language directly influencing the storage and representation thereof. The dissertation argues that metaphors, as conventionalized cognitive structures, are themselves highly influenced by frequency effects, and that metaphorical cross-domain mappings exist in the mind as conceptual schemata. Two corpus-based methods for assessing the frequency of overall metaphorical mappings are presented, both based on the use of key terms, attained using a survey method, for metaphorical source domains. These findings inform the hypotheses of a series of three experiments which test three key predictions of the view that metaphors are affected by frequency: that frequent metaphors should be more productive, accessible, and acceptable than infrequent ones. Both the corpus and experimental approaches, as well as data from previous research on metaphor at varying levels of conventionalization, support the view that metaphors are a usage-based phenomenon. The properties of various types of metaphorical utterances (e.g., idioms and novel metaphors) are best accounted for as arising from the interaction of the conceptual schemata that license cross-domain mappings, and syntactic schemata that link meanings to syntactic templates

Unsteady aerodynamics of an oscillating cascade in a compressible flow field

Fundamental experiments were performed in the NASA Lewis Transonic Oscillating Cascade Facility to investigate and quantify the unsteady aerodynamics of a cascade of biconvex airfoils executing torsion-mode oscillations at realistic reduced frequencies. Flush-mounted, high-response miniature pressure transducers were used to measure the unsteady airfoil surface pressures. The pressures were measured for three interblade phase angles at two inlet Mach numbers, 0.65 and 0.80, and two incidence angles, 0 and 7 deg. The time-variant pressures were analyzed by means of discrete Fourier transform techniques, and these unique data were then compared with predictions from a linearized unsteady cascade model. The experimental results indicate that the interblade phase angle had a major effect on the chordwise distributions of the airfoil surface unsteady pressure, and that reduced frequency, incidence angle, and Mach number had a somewhat less significant effect

Junior Recital, Jacob Sanford, clarinet

The presentation of this junior recital will fulfill in part the requirements for the Bachelor of Music degree in Education. Jacob Sanford studies clarinet with Dr. Tiffany Valvo