Toward comparing experiment and theory for corroborative research on hingeless rotor stability in forward flight

For flap lag stability of isolated rotors, experimental and analytical investigations were conducted in hover and forward flight on the adequacy of a linear quasisteady aerodynamics theory with dynamic flow. Forward flight effects on lag regressing mode were emphasized. A soft inplane hingeless rotor with three blades was tested at advance ratios as high as 0.55 and at shaft angles as high as 20 deg. The 1.62 m model rotor was untrimmed with an essentially unrestricted tilt of the tip path plane. In combination with lag natural frequencies, collective pitch settings and flap lag coupling parameters, the data base comprises nearly 1200 test points (damping and frequency) in forward flight and 200 test points in hover. By computerized symbolic manipulation, a linear model was developed in substall to predict stability margins with mode identification. To help explain the correlation between theory and data it also predicted substall and stall regions of the rotor disk from equilibrium values. The correlation showed both the strengths and weaknesses of the theory in substall ((angle of attack) equal to or less than 12 deg)

A review of dynamic inflow and its effect on experimental correlations

A review is given of the relationship between experimental data and the development of modern dynamic-inflow theory. Some of the most interesting data, first presented 10 years ago at the Dynamic Specialist's Meeting, is now reviewed in light of the newer theories. These pure blade-flapping data correlate very well with analyses that include the new dynamic inflow theory, thus verifying the theory. Experimental data are also presented for damping with coupled inplane and body motions. Although inclusion of dynamic inflow is often required to correlate this coupled data, the data cannot be used to verify any particular dynamic inflow theory due to the uncertainties in modeling the inplane degree of freedom. For verification, pure flapping is required. However, the coupled data do show that inflow is often important in such computations

Computational aspects of helicopter trim analysis and damping levels from Floquet theory

Helicopter trim settings of periodic initial state and control inputs are investigated for convergence of Newton iteration in computing the settings sequentially and in parallel. The trim analysis uses a shooting method and a weak version of two temporal finite element methods with displacement formulation and with mixed formulation of displacements and momenta. These three methods broadly represent two main approaches of trim analysis: adaptation of initial-value and finite element boundary-value codes to periodic boundary conditions, particularly for unstable and marginally stable systems. In each method, both the sequential and in-parallel schemes are used and the resulting nonlinear algebraic equations are solved by damped Newton iteration with an optimally selected damping parameter. The impact of damped Newton iteration, including earlier-observed divergence problems in trim analysis, is demonstrated by the maximum condition number of the Jacobian matrices of the iterative scheme and by virtual elimination of divergence. The advantages of the in-parallel scheme over the conventional sequential scheme are also demonstrated

Concepts for a theoretical and experimental study of lifting rotor random loads and vibrations, Phase 2

A comparison with NASA conducted simulator studies has shown that the approximate digital method for computing rotor blade flapping responses to random inputs, tentatively suggested in Phase I Report, gives with increasing rotor advance ratio the wrong trend. Consequently, three alternative methods of solution have been considered and are described: (1) an approximate method based on the functional relation between input and output double frequency spectra, (2) a numerical method based on the system responses to deterministic inputs and (3) a perturbation approach. Among these the perturbation method requires the least amount of computation and has been developed in two forms - the first form to obtain the response correlation function and the second for the time averaged spectra of flapping oscillations

An experimental and analytical investigation of isolated rotor flap-lag stability in forward flight

For flap-lag stability of isolated rotors, experimental and analytical investigations are conducted in hover and forward flight on the adequacy of a linear quasisteady aerodynamics theory with dynamic inflow. Forward flight effects on lag regressing mode are emphasized. A soft inplane hingeless rotor with three blades is tested at advance ratios as high as 0.55 and at shaft angles as high as 20 degrees. In combination with lag natural frequencies, collective pitch settings and flap-lag coupling parameters, the data base comprises nearly 1200 test points (damping and frequency) in forward flight and 200 test points in hover. By computerized symbolic manipulations, an analytic model is developed in substall to predict stability margins with mode identification. It also predicts substall and stall regions to help explain the correlation between theory and data

Diversity, Distribution and Evolution of the Planktonic Diatom Family Chaetocerotaceae

The number and abundance of diatom species in environmental samples are counted traditionally by means of light microscopy (LM). However, recognizing –let alone, counting- species is often challenging because of the existence of cryptic species and intraspecific phenotypic plasticity. Proper characterization requires isolation of cells, growing them into monoclonal cultures, and characterizing the cultures genetically and morphologically. However, not all species grow in culture, featureless ones are less likely to be isolated, and the procedure is laborious. High-throughput sequencing (HTS) metabarcoding bypasses morphology; DNA is collected from environmental samples, a particular marker sequenced, and the resulting sequences sorted into clusters or terminal clades assumed to represent species. Yet, reference barcodes of taxonomically validated species are needed to identify these clades. This exercise is the main aim of my thesis. Since it is impossible to do this for all the diversity within a PhD thesis project, we selected Chaetocerotaceae, an abundant and diverse family of marine planktonic diatoms, containing two genera: Chaetoceros and Bacteriastrum. Its members uniquely share setae; thin siliceous tubes emerging from the valve corners, facilitating detection in samples. Strains were obtained from the Gulf of Naples (GoN), from Central Chile and Roscoff – at sites for which LTER time series data are available. A total of 270 strains were obtained from these sites, and their 18S- and partial 28S rDNA sequences and morphological information gathered. The strains grouped into 60 genetically distinct species, thus providing a dataset of validated Chaetocerotacean 18S reference barcodes. Inferred molecular phylogenies showed monophyletic Chaetocerotaceae as well as monophyletic Bacteriastrum inside paraphyletic Chaetoceros, and the presence of cryptic diversity. To start with taxonomic updates, the species C. sporotruncatus and C. dichatoensis were described within the C. socialis species-complex based on spore morphology and sequence differences. Several rDNA sequences contained spliceosomal introns (ca. 100bp) and/or group-I introns (ca. 400bp). Phylogenies inferred from the introns did not corroborate rDNA phylogenies, suggesting horizontal gene transfer. Presence/absence of introns in conspecific strains sampled in different seasons suggests population differentiation between these seasons. A HTS dataset consisting of V4-sequences (part of 18S) from 48 seawater samples taken over the seasons in the GoN revealed 76 terminal clades of which 46 grouped with a reference barcode. Some of these species occur year-round whereas most others are seasonal. Surprisingly, of the 30 clades belonging to unknown Chaetocerotacean species, two appear to be among the most abundant in the GoN

A detail review of types of Kshara with special emphasis on Rasashastra

Kshara (Alkali) has been in existence from ancient times. Their importance lies in the fact that they can be comfortably utilized to replace certain surgical procedures. Its properties are compared with that of Agni (fire) and yet it has its own special features too. Like although it is Ushna (hot) it is Sheeta (cool) in touch, although it has cutting and corroding property it can be utilized to be consumed orally as a medicine. And this is what makes it special. It is derived from plant, animal as well mineral sources. Its potency can be changed by combining various Kshara as per the need and requirement of the patient. Many Kshara’s have been described in our texts. This article aims at compiling those Kshara and elaborating their properties. There are also few Kshara which have not been classified as Kshara but which possess all the properties of Kshara, such Dravya have also been described in the current article. It is a review of Kshara and their properties as described in various Ayurvedic texts with special emphasis on Rasashastra (Iatrochemistry of Ayurveda) texts