Student Number : 9910049F - MSc (Eng) dissertation - School of Mechanical, Industrial and Aeronautical Engineering - Faculty of Engineering and the Built Environment / Cavitation was generated in tap water samples by the transmission of tension waves into the liquid, using a hydrodynamic shock tube. The liquid cavitated at absolute negative pressures of about -1 bar. Simulations of bubble responses showed qualitative agreement with experimental observations of oscillatory growth and collapse cycles. Pressure records showed secondary pressure pulsations, confirming the oscillatory nature of the collapse at each rise in pressure. More quantitative comparison of theory and photographic records would require a camera with a higher capture rate. Experiments using another experimental facility involved liquid compression waves with peak static pressures of up to about 1 MPa, which were transmitted from a conventional gas shock tube into a liquid section and were intended to be reflected at the free surface as expansion waves. These experiments were unsuccessful in producing absolute negative pressures or cavitation that was visible through an optical observation section. This was attributed to transition layer effects and pulse attenuation, which contributed to lowering of the peak negative pressure behind the expansion wave, as well as the depth of the transducer and observation section below the free surface, which may have been too low for the peak tension to be superimposed on the lower pressure behind the incident compression wave. Pressure records suggested that, for lower driver pressures, cavitation occurred below the observation section, although this could not be verified optically.

Experiments are presented in which the diffuse interface between two gases is made Rayleigh-Taylor unstable by interaction with a rarefaction wave. The apparatus used consists of a test section where the counter-flow of light and heavy gases generates a diffuse, stably stratified interface. A tank attached to the bottom of the apparatus is evacuated, and when an appropriate pressure is reached, the interface is perturbed using either a horizontal or a vertical oscillation technique to produce 2D, 3D, and multi-mode perturbations. A solenoid plunger fires an arrowhead which ruptures a membrane, generating a rarefaction wave that travels upward toward the interface. When the rarefaction wave impacts the interface, the interface accelerates down toward the vacuum tank, and the Rayleigh-Taylor instability and mixing develop in the test section. The instability evolution and mixing are recorded using high-speed CMOS cameras and planar laser Mie scattering of smoke particles seeded in the heavy gas. Additional visualization is undertaken with a high-speed shadowgraph system using three CMOS cameras. Interface diffusion thicknesses are recorded using the Rayleigh scattered light of an unexpanded laser beam. Simulations are conducted using a 1D numerical characteristics code based on the method of Hoskin (Meth. Comp. Physics, 3, 1964), and using the LLNL research hydrodynamics code Miranda (Cook, Phys. Fluids, 19, 2007). This 1D code produces Lagrangian interface trajectories while the 2D and 3D simulations using Miranda calculate the growth of perturbations. The theory of Chandrasekhar (Chandrasekhar, Proc. Camb. Phil. Soc., 51, 1955) is extended to capture the effects of diffuse interfaces while including viscosity, and dispersion curves are solved for numerically using a Riccati technique. These solutions show that the method of Duff et al. (Phys. Fluids, 5, 1962) may not accurately describe the growth of single modes for large wavenumbers. For large wavenumbers, when the interface has a large diffusion thickness, perturbations are found to grow with the linear growth rate n = 2Ag/(√πv₀δk²), where A is the Atwood number, g is the acceleration, v₀ is the average kinematic viscosity, δ is the thickness of the interface, and k is the wavenumber of the perturbation. Flat interface experiments exhibit predictable acceleration profiles, but the tail of the rarefaction wave appears at late times reducing the duration of acceleration. Single-mode experiments are conducted for four Atwood numbers including CO₂/SF₆ with A = 0.49, Air/SF₆ with A = 0.63, He/CO₂ with A = 0.82, and He/SF₆ with A = 0.94. Early time results compare well with linear stability theory when non-constant acceleration and diffusion thickness are accounted for. Simulations show good agreement with experiments into the non-linear growth phase. The CO₂/SF₆ and Air/SF₆ experiments show terminal velocity behavior where buoyancy is balanced by drag, but produce Froude numbers larger than those predicted by the Goncharov model (Phys. Rev. Lett., 88, 2002). Using the Mikaelian model (Phys. Fluids, 21, 2009), improved asymptotic Froude numbers are found. The He/CO₂ and He/SF₆ experiments exhibit free-fall behavior, accelerating freely without external forces, with spike amplitudes proportional to the displacement of the unperturbed interface. Single-mode experiments conducted with 3D perturbations using CO₂/SF₆ and Air/SF₆ show good agreement with linear stability theory when non-constant acceleration and diffusion thickness are accounted for. Simulations and the model of Mikaelian predict the growth of the spikes up until late time, while the 3D bubbles reach a terminal velocity more quickly than in simulations. Multi-mode experiments were conducted using Air/SF₆. Multi-mode experiments exhibit nearly t² growth at early times which decays. Using extraction techniques that account for variable acceleration, alpha values are found between ɑ = 0.02 and ɑ = 0.04. These alpha values are lower than are seen for most experiments, but are similar to ɑ values seen in miscible experiments.

Heat transfer of two-dimensional, hydrodynamically developed, thermally developing, single phase, laminar flow inside a microtube is studied analytically with constant wall temperature thermal boundary condition. The flow is assumed to be incompressible and thermo-physical properties of the fluid are assumed to be constant. Viscous dissipation and the axial conduction are included in the analysis. Rarefaction effect is imposed to the problem via velocity slip and temperature jump boundary conditions for the slip flow regime. The temperature distribution is determined by solving the energy equation together with the fully developed velocity profile. Analytical solutions are obtained for the temperature distribution and local and fully developed Nusselt number in terms of dimensionless parameters / Peclet number, Knudsen number, Brinkman number, and the parameter &amp / #954 / . The results are verified with the well-known ones from literature.

Acute kidney injury (AKI) is a major complication in hospitalized patients and is associated with elevated mortality rates. Numerous recent studies indicate that AKI also significantly increases the risk of chronic kidney disease (CKD), end-stage renal disease (ESRD), hypertension, cardiovascular disease, and mortality in those patients who survive AKI. Moreover, the risk of ESRD and mortality after AKI is substantially higher in patients with preexisting CKD. However, the underlying mechanisms by which AKI and CKD interact to promote ESRD remain poorly understood. The recently developed models that superimpose AKI on rodents with preexisting CKD have provided new insights into the pathogenic mechanisms mediating the deleterious interactions between AKI and CKD. These studies show that preexisting CKD impairs recovery from AKI and promotes the development of mechanisms of CKD progression. Specifically, preexisting CKD exacerbates microvascular rarefaction, failed tubular redifferentiation, disruption of cell cycle regulation, hypertension, and proteinuria after AKI. The purpose of this review is to discuss the potential mechanisms by which microvascular rarefaction and hypertension contribute to impaired recovery from AKI and the subsequent progression of renal disease in preexisting CKD states.

Yes / The existing analytical solutions of dam-break flow do not consider simultaneously the effects of wet downstream bottom and bed slope on the dam-break wave propagation. In this study, a new analytical solution for the shallow-water equations (SWE) is developed to remove this limitation to simulate the wave caused by an instantaneous dam-break. The approach adopts the method of characteristics and has been applied to simulate the dam-break flows with different downstream water depths and slopes. The analytical solutions have been compared with predictions by the lattice Boltzmann method and the agreement is good. Although the proposed analytical solution treats an idealized case, it is nonetheless suitable for assessing the robustness and accuracy of numerical models based on the SWE without the frictional slope. / The National Key Research and Development Program of China (Grant No: 2018YFC1505000), National Natural Science Foundation of China (Grant Nos: 51879179; 51579166) and Sichuan Science and Technology Program (No. 2019JDTD0007); Open Fund from the State Key Laboratory of Hydraulics and Mountain River Engineering, Sichuan University (SKHL1809). .

Fluid damping arising from squeeze film flow of air or some inert gas trapped between an oscillating micro mechanical structure, such as a beam or a plate, and a fixed substrate often dominates the other energy dissipation mechanisms in silicon based MEM devices. As a consequence, it has maximum effect on the resonant response or dynamic response of the device. Unfortunately, modelling of the squeeze film flow in most MEMS devices is quite complex because of several factors unique to MEMS structures. In this thesis, we set out to study the effect of these factors on squeeze film flow. First we list these factors and study each of them in the context of a particular application, using experimental measurements, extensive numerical simulations, and analytical modelling for all chosen factors. We consider five important factors. The most important factor perhaps is the effect of rarefaction that is dominant when a device is vacuum packed with low to moderate vacuum, typical for MEMS packaging. The second problem is to investigate and model the effect of perforations which are usually provided for efficient etching of the sacrificial layer during fabrication of the suspended structures. The third problem is to consider the effect of non-uniform deflection of the structure such as those in MEMS cantilever beams and model its effect on the squeeze film. The fourth effect studied is the influence of different boundary conditions such as simple, fully open and partially closed boundaries around the vibrating structure on the characteristics of the squeeze film flow. The fifth problem undertaken is to analyze the effect of high operating frequencies on the squeeze film damping. In the first problem, the rarefaction effect is studied by performing experiments under varying pressures. Depending on the ambient pressure or the size of the gap between the vibrating and the fixed structure, the fluid flow may fall in any of the flow regimes, ranging from continuum flow to molecular flow, and giving a wide range of dissipation. The relevant fluid flow characteristics are determined by the Knudsen number, which is the ratio of the mean free path of the gas molecule to the characteristic flow length of the device. This number is very small for continuum flow and reasonably big for molecular flow. Here, we study the effect of fluid pressure on the squeeze film damping by carrying out experiments on a MEMS device that consists of a double gimbaled torsional resonator. Such devices are commonly used in optical cross-connects and switches. We vary fluid pressure to make the Knudsen number go through the entire range of continuum flow, slip flow, transition flow, and molecular flow. We experimentally determine the quality factor of the torsional resonator at different air pressures ranging from 760 torr to 0.001 torr. The variation of this pressure over six orders of magnitude ensures the required rarefaction to range over all flow conditions. Finally, we get the variation of the quality factor with pressure. The result indicates that the quality factor, Q, follows a power law, Q P-r, with different values of the exponent r in different flow regimes. To numerically model the effect of rarefaction, we propose the use of effective viscosity in Navier-Stokes equation. This concept is validated with analytical results for a simple case. It is then compared with the experimental results presented in this thesis. The study shows that the effective viscosity concept can be used effectively even for the molecular regime if the air-gap to length ratio is sufficiently small (h0/L < 0.01). However, as this ratio increases, the range of validity decreases. Next, a semianalytical approach is presented to model the rarefaction effect in double-gimballed MEMS torsion mirror. In this device, the air gap thickness is 80 µm which is comparable to the lateral dimension 400 µm of the oscillating plate and thus giving the air-gap to length ratio of 0.2. As the ratio 0.2 is much greater than 0.01, the conventional Reynolds equation cannot be used to compute the squeeze film damping. Consequently, we find the effective length of an equivalent simple mirror corresponding to the motion about the two axes of the mirror such that the Reynolds equation still holds. After finding the effective length, we model the rarefaction effect by incorporating effective viscosity which is based on different models including the one proposed in this paper. Then we compare the analytical solution with the experimental result and find that the proposed model not only captures the rarefaction effect in the slip, transition and molecular regimes but also couples well with the non-fluid damping in the intrinsic regime. For the second problem, several analytical models exist for evaluating squeeze film damping in rigid rectangular perforated MEMS structures. These models vary in their treatment of losses through perforations and squeezed film, in their assumptions of compressibility, rarefaction and inertia, and their treatment of various second order corrections. We present a model that improves upon previously reported models by incorporating more accurate losses through holes proposed by Veijola and treating boundary cells and interior cells differently as proposed by Mohite et al. The proposed model is governed by a modified Reynolds equation that includes compressibility and rarefaction effect. This equation is linearized and transformed to the standard two-dimensional diffusion equation using a simple mapping function. The analytical solution is then obtained using Green’s function. The solution thus obtained adds an additional term Γ to the damping and spring force expressions derived by Blech for compressible squeeze flow through non-perforated plates. This additional term contains several parameters related to perforations and rarefaction. Setting Γ = 0, one recovers Blech’s formulas. We benchmark all the models against experimental results obtained for a typical perforated MEMS structure with geometric parameters (e.g., perforation geometry, air gap, plate thickness) that fall well within the acceptable range of parameters for these models (with the sole exception of Blech’s model that does not include perforations but is included for historical reasons). We compare the results and discuss the sources of errors. We show that the proposed model gives the best result by predicting the damping constant within 10% of the experimental value. The approximate limit of maximum frequencies under which the formulas give reasonable results is also discussed. In the third problem, we study the effect of elastic modeshape during vibration on the squeeze film flow. We present an analytical model that gives the values of squeeze film damping and spring coefficients for MEMS cantilever resonators taking into account the effect of flexural modes of the resonator. We use the exact modeshapes of a 2D cantilever plate to solve for pressure in the squeeze film and then derive the equivalent damping and spring coefficient relations from the back force calculations. The relations thus obtained can be used for any flexural mode of vibration of the resonators. We validate the analytical formulas by comparing the results with numerical simulations carried out using coupled finite element analysis in ANSYS, as well as experimentally measured values from MEMS cantilever resonators of various sizes and vibrating in different modes. The analytically predicted values of damping are, in the worst case, within less than 10% of the values obtained experimentally or numerically. We also compare the results with previously reported analytical formulas based on approximate flexural modeshapes and show that the proposed model gives much better estimates of the squeeze film damping. From the analytical model presented here, we find that the squeeze film damping drops by 84% from the first mode to the second mode in a cantilever resonator, thus improving the quality factor by a factor of six to seven. This result has significant implications in using cantilever resonators for mass detection where a significant increase in quality factor is obtained only by using vacuum. In the fourth and fifth problem, the effects of partially blocked boundary condition and high operating frequencies on squeeze films are studied in a MEMS torsion mirror with different boundary conditions. For the structures with narrow air-gap, Reynolds equation is used for calculating squeeze film damping, generally with zero pressure boundary conditions on the side walls. This procedure, however, fails to give satisfactory results for structures under two important conditions: (a) for an air-gap thickness comparable to the lateral dimensions of the micro structure, and (b) for non-trivial pressure boundary conditions such as fully open boundaries on an extended substrate or partially blocked boundaries that provide side clearance to the fluid flow. Several formulas exist to account for simple boundary conditions. In practice, however, there are many micromechanical structures, such as torsional MEMS structures, that have non-trivial boundary conditions arising from partially blocked boundaries. The most common example is the double-gimballed MEMS torsion mirror of rectangular, circular, or hexagonal shape. Such boundaries usually have clearance parameters that can vary due to fabrication. These parameters, however, can also be used as design parameters if we understand their role on the dynamics of the structure. We take a MEMS torsion mirror as an example device that has large air-gap and partially blocked boundaries due to static frames. Next we model the same structure in ANSYS and carry out CFD (computational fluid dynamics) analysis to evaluate the stiffness constant K, the damping constant C, as well as the quality factor Q due to the squeeze film. We compare the computational results with experimental results and show that without taking care of the partially blocked boundaries properly in the computational model, we get unacceptably large errors. Subsequently, we use the CFD calculations to study the effect of two important boundary parameters, the side clearance c, and the flow length s, that specify the partial blocking. We show the sensitivity of K and C on these boundary design parameters. The results clearly show that the effect of these parameters on K and C is substantial, especially when the frequency of excitation becomes close to resonant frequency of the oscillating fluid and high enough for inertial and compressibility effects to be significant. Later, we present a compact model to capture the effect of side boundaries on the squeeze film damping in a simple rectangular torsional structure with two sides open and two sides closed. The analytical model matches well with the numerical results. However, the proposed analytical model is limited to low operating frequencies such that the inertial effect is negligible. The emphasis of this work has been towards developing a comprehensive understanding of different significant factors on the squeeze film damping in MEMS devices. We have proposed various ways of modelling these effects, both numerically as well as analytically, and shown the efficacy of these models by comparing their predictive results with experimental results. In particular, we think that the proposed analytical models can help MEMS device designers by providing quick estimates of damping while incorporating complex effects in the squeeze film flow. The contents of the thesis may also be of interest to researchers working in the area of microfluidics and nanofluidics.

Interações positivas entre plantas têm sido demonstradas em várias comunidades em todo mundo, as quais desempenham papéis importantes na coexistência de espécies, produtividade e diversidade específica. Nesse estudo, avaliamos a influência de Bromelia balansae Mez sobre a riqueza específica, composição, abundância e diversidade de espécies lenhosas nos sub-bosques florestais e nas bordas externas de três afloramentos rochosos com cobertura herbácea presentes no Parque Estadual do Turvo, sul do Brasil. Estabelecemos 15 pares de unidades amostrais (u.a.) em cada afloramento rochoso e igual número na floresta, totalizando 180 u.a.. Consideramos as rosetas das bromélias como u.a. circulares e, como controle, instalamos u.a. correspondentes em áreas sem bromélias. Cada u.a. foi descrita pela abundância de indivíduos juvenis de espécies lenhosas. Para analisar o efeito de B. balansae sobre a riqueza, utilizamos curvas de rarefação baseados nas u.a.. Avaliamos também o efeito sobre a abundância de espécies no afloramento e na floresta utilizando ANOVAs com permutação. As curvas de rarefação revelaram uma diferença significativa da riqueza específica entre as u.a. nos afloramentos onde B. balansae está presente daquelas onde não está. Porém, na floresta, a riqueza de espécies entre u.a. com e sem B. balansae não apresentou diferença significativa. Nos campos rupestres, a presença de B. balansae influenciou positivamente a abundância de espécies em comparação às áreas controle. Na floresta, porém, não encontramos diferenças entre u.a. com e sem B. balansae. / Positive interactions among plants have been demonstrated in several communities around the world and play important roles in maintaining species coexistence, productivity and species diversity. In this study we evaluated the influence of Bromelia balansae Mez on species richness, composition, abundance and diversity of trees and shrubs in the forest understory and on the outer edge of rock outcrops present on Turvo State Park, Rio Grande do Sul, Brazil. The sampling was done in three outcrop areas, which constituted replicas, to evaluate the influence of the presence of B. balansae on woody species. To analyze the effect on the richness of bromeliads, we used rarefaction curves based on sampling units (s.u.). We also evaluated the effect on the abundance of species in outcrop and forest with ANOVAs using permutation. Rarefaction curves showed a significant difference in species richness between s.u. of the outcrops where B. balansae was present and the those without the species. However, the s.u. in the forest, species richness between s.u. with and without B. balansae showed no significant difference. In rocky fields, the presence of B. balansae has positively influenced the abundance of species in comparison to the control areas. In the forest, however, no differences between s.u. with and without B. balansae.

Heat transfer analysis of two-dimensional, incompressible, constant property, hydrodynamically developed, thermally developing, single phase laminar flow in microtubes and microchannels between parallel plates with negligible axial conduction is performed for constant wall temperature and constant wall heat flux thermal boundary conditions for slip flow regime. Fully developed velocity profile is determined analytically, and energy equation is solved by using finite difference method for both of the geometries. The rarefaction effect which is important for flow in low pressures or flow in microchannels is imposed to the boundary conditions of the momentum and energy equations. The viscous dissipation term which is important for high speed flows or flows in long pipelines is included in the energy equation. The effects of rarefaction and viscous heating on temperature profile and local Nusselt number are discussed. The results of the numerical method are verified with the well-known analytical results of the flow in macrochannels (i.e. Kn =0, Br =0) and with the available analytical results of flow in microchannels for simplified cases. The results show significant deviations from the flow in macrochannels.

Made available in DSpace on 2016-06-02T19:32:14Z (GMT). No. of bitstreams: 1 6527.pdf: 2310287 bytes, checksum: 6b506abf65a5fa7b4ec9bb3b44d34a22 (MD5) Previous issue date: 2014-08-14 / Financiadora de Estudos e Projetos / Species kept in captivity are of great importance for in situ conservation of natural populations. In order to fulfill this role, they need to be properly managed with the aim to avoid the consequences of a captive environment, such as: loss of genetic diversity, inbreeding depression, accumulation of deleterious alleles and genetic adaptation to captivity (the first three due to the small number of breeding stock). Thus, with the aim to test founder effects in captive &#8213;populations&#8214;, we used as study model the spectacled bears from Brazilian zoos. This &#8213;population&#8214; consists of twenty-one bears found in eight zoos along the country, which are originated from just twelve founding individuals. To test a possible founder effect, we analyzed twelve heterologous microsatellite loci for all the specimens of the species in Brazil. Results for the number of alleles and allelic richness obtained through the rarefaction method showed that spectacled bears in captivity have reduced levels of allelic richness in relation to three natural populations (Colombia, Ecuador and Venezuela) studied by other authors; suggesting that bears from Brazilian zoos suffered the consequences of a founding effect, as they have only a fraction of the gene pool of the ancestral population. From the information present in the studbook was possible to verify that there are two families of spectacled bears, and according to the individuals´s multilocus genotypes, we found alleles that are present in a same family and absent in the other. Regarding the kinship, there was a discrepancy in the results with the molecular estimators through the softwares ML-Relate and Coancestry and the information given by the institutions. The information obtained in this work are fundamental to the ex situ conservation program in Brazil with the objective of maintain as high as possible the genetic diversity for future reintroduction plans of the species in nature. / Espécies mantidas em cativeiro são de grande importância na conservação in situ de populações naturais. A fim de que possam desempenhar este papel é necessário que sejam devidamente manejadas, para que as consequências que o cativeiro traz sejam evitadas, como por exemplo: perda de diversidade genética, depressão endogâmica, acúmulo de alelos deletérios e adaptação genética ao cativeiro (as três primeiras devido ao pequeno número de espécimes dos plantéis). No Brasil, uma espécie de mamífero que vem sendo criada em cativeiro desde 1970 e que passou por um efeito fundador, é o urso de óculos (Tremarctos ornatus). O plantel existente hoje totaliza o número de vinte e um ursos, encontrados em oito zoológicos do país, o qual se originou de apenas doze indivíduos fundadores. Para avaliar as consequências de um conhecido efeito fundador, analisamos doze locos heterólogos de microssatélites para todos os exemplares da espécie nos zoos do país, através de amostragem não-invasiva. Resultados referentes ao número de alelos e à riqueza alélica obtida por meio do método de rarefação mostraram que os ursos de óculos de cativeiro possuem valores reduzidos de riqueza alélica em relação a três populações naturais (Colômbia, Equador e Venezuela) estudadas por outros autores; sugerindo que os ursos dos zoológicos brasileiros sofreram as consequências de um efeito fundador, pois possuem apenas uma fração do pool gênico da população ancestral. A partir das informações presentes no studbook foi possível verificar que existem duas famílias de ursos de óculos, e de acordo com os genótipos multilocos dos indivíduos, encontramos alelos que estão presentes em uma mesma família e ausentes na outra. Em relação ao parentesco, houve uma discrepância nos resultados encontrados com os estimadores moleculares através dos softwares ML-Relate e Coancestry e o histórico cedido pelas instituições. As informações obtidas em nosso trabalho, portanto, são fundamentais para que os ursos encontrados nos zoológicos do Brasil possam participar na formação de casais em futuros programas de reprodução ex situ com o propósito de serem utilizados em planos de reintrodução da espécie na natureza.

Interações positivas entre plantas têm sido demonstradas em várias comunidades em todo mundo, as quais desempenham papéis importantes na coexistência de espécies, produtividade e diversidade específica. Nesse estudo, avaliamos a influência de Bromelia balansae Mez sobre a riqueza específica, composição, abundância e diversidade de espécies lenhosas nos sub-bosques florestais e nas bordas externas de três afloramentos rochosos com cobertura herbácea presentes no Parque Estadual do Turvo, sul do Brasil. Estabelecemos 15 pares de unidades amostrais (u.a.) em cada afloramento rochoso e igual número na floresta, totalizando 180 u.a.. Consideramos as rosetas das bromélias como u.a. circulares e, como controle, instalamos u.a. correspondentes em áreas sem bromélias. Cada u.a. foi descrita pela abundância de indivíduos juvenis de espécies lenhosas. Para analisar o efeito de B. balansae sobre a riqueza, utilizamos curvas de rarefação baseados nas u.a.. Avaliamos também o efeito sobre a abundância de espécies no afloramento e na floresta utilizando ANOVAs com permutação. As curvas de rarefação revelaram uma diferença significativa da riqueza específica entre as u.a. nos afloramentos onde B. balansae está presente daquelas onde não está. Porém, na floresta, a riqueza de espécies entre u.a. com e sem B. balansae não apresentou diferença significativa. Nos campos rupestres, a presença de B. balansae influenciou positivamente a abundância de espécies em comparação às áreas controle. Na floresta, porém, não encontramos diferenças entre u.a. com e sem B. balansae. / Positive interactions among plants have been demonstrated in several communities around the world and play important roles in maintaining species coexistence, productivity and species diversity. In this study we evaluated the influence of Bromelia balansae Mez on species richness, composition, abundance and diversity of trees and shrubs in the forest understory and on the outer edge of rock outcrops present on Turvo State Park, Rio Grande do Sul, Brazil. The sampling was done in three outcrop areas, which constituted replicas, to evaluate the influence of the presence of B. balansae on woody species. To analyze the effect on the richness of bromeliads, we used rarefaction curves based on sampling units (s.u.). We also evaluated the effect on the abundance of species in outcrop and forest with ANOVAs using permutation. Rarefaction curves showed a significant difference in species richness between s.u. of the outcrops where B. balansae was present and the those without the species. However, the s.u. in the forest, species richness between s.u. with and without B. balansae showed no significant difference. In rocky fields, the presence of B. balansae has positively influenced the abundance of species in comparison to the control areas. In the forest, however, no differences between s.u. with and without B. balansae.