Fluid flow in a duct of varying cross-section Essay Example

Fluid flow in a duct of varying cross-section Paper The purpose of this experiment was to demonstrate the relation between pressure and fluid velocity in a duct of varying cross-sectional area. This experiment is carried out on the basis of conservation of mass and energy. Both the Bernoullis equation and the Continuity equation are essential analytical tools used for the analysis of problems in the subject of Mechanics of Fluids, in this case flow of fluid in the venturi. The constant flow rate in the varying cross-section duct suggests that the fluid velocity and pressure should compensate this varying cross-section accordingly. As the varying cross-section becomes convergent the velocity and pressure of the fluid is at its highest value. Thus signifying that the at the divergent or diffuser end the velocity and pressure of the fluid should progressively go back to its original values. Theory The continuity equation states that the fluid must remain constant and is in essence a state of the conservation of mass. For an incompressible flow, which involves a liquid or a gas at low velocity, the equation of continuity is; AV = Q = CONSTANT Where; A Cross-Sectional Area V Mean Velocity. Q Volumetric Flow Rate Bernoullis theorem shows the principle of conservation of energy for a steady flow. For an inviscid or frictionless flow, the following equation is applied; Where; P Static Pressure p Density Z Elevation above an arbitrary value V- Fluid velocity Bernoullis equation shows that the sum of the three quantities is a constant. In this experiment, the duct is horizontal; therefore, there is no gravitational effect. In this case we could ignore the gz term. It is then convenient to express the static pressure, P as an equivalent head of liquid h (=p/? We will write a custom essay sample on Fluid flow in a duct of varying cross-section specifically for you for only $16.38 $13.9/page Order now We will write a custom essay sample on Fluid flow in a duct of varying cross-section specifically for you FOR ONLY $16.38 $13.9/page Hire Writer We will write a custom essay sample on Fluid flow in a duct of varying cross-section specifically for you FOR ONLY $16.38 $13.9/page Hire Writer g), and hence the Bernoullis equation becomes: h + v2 = CONSTANT 2g Apparatus The set-up consists of a pipe of constant diameter, then a short contraction to a narrow throat followed by a long diffuser and finally a pipe of the same size as the original one. This arrangement is referred to as a Venturi. Experimental Procedure Start the pump and initiate a flow of water through the test section. Regulate the flow using the flow meter to 46 Litres/Min. Allow the some few minutes for the flow to regulate and then take manometer readings for tapings 1 to 10. Repeat the procedure for different flow rates; 34 Litres/Min. and 24 Litres/Min. Results The table shows the tapping numbers, the distance from the tapping number 1 and the cross-section diameter at each tapping Tapping Number 1 2 3 4 5 6 7 8 9 10 Distance, x (mm) 0 80 122 164 238 312 386 460 534 607 Diameter, d (mm) 41 41 28 15. 5 21. 4 27. 8 34. 1 40. 5 40. 5 40. 5 Discussion From analysing the results we can see that as cross-sectional area decreases the velocity of the fluid inside increases to maintain continuity and constant volumetric flow. The velocity of the fluid reaches its maximum at the throat where the venturi converges so that the cross-sectional area is at its minimum value. Graph One represents the change in static head (pressure difference) along the duct. From the continuity equation; smaller the area, greater the velocity of the flow and hence the greater the velocity, lower the pressure. This can be clearly seen from the graph. Taping number 4 shows the greatest pressure difference in each flow rate. This is because it is the minimum cross-sectional area of the duct. The pressure head then decreases as the cross-sectional area increases (Tapings 5 10). Different flow rate also have different change in pressure head at each tapping. In this case, the change in pressure head is the greatest when the flow rate is at 46Litres/Min. Hence, it can be stated that fluids at high velocity experience low pressure. Therefore, it can concluded from the graph that as the cross-sectional area reduces, the velocity increases and hence the pressure reduces. Graph Two, it is clearly noted that the variations of the normalised total head are very similar to the normalised static head. The normalised static head given by the formula [1-(d1/dn)4] represents the theoretical values of fluid flow. However, the values do not return to the zero value which shows that there is energy loss along the duct. This may be due to friction. The normalised head graphs vary slightly from the theoretical graphs which may be due high friction at higher velocities. There is usually a noted difference in readings and analysis of experiments compared to theory. This take place due to several reasons; more common, the human reading error. There is an allowance of certain percentage to give the accuracy of value to be with a confined range. Reading error: i 0. 1cm Flow meter: i 1Litre/Min Graph Three shows the variant of normalised static pressure along the duct. We can visualise this from the flow rates of 34 l/min and 46 l/min after the decrease in pressure there is a rise in pressure variation then it falls again. This can be a human error created by misread readings or a fault with the apparatus. The variation should in theory look more like the 26 l/min flow plot. Error Analysis Variations between practical and theoretical results are common in most experiments. Due to the conditions of our investigations our results are always suspect to error, which is why an error analysis calculation is used to give us a clearer idea of how accurate our results are. The main errors are usually caused by human error due to misread readings. Error build up due to use of approximated values carried out in calculations and errors due to incorrect calibration of equipment are also key factors. Every measurement made is susceptible to error. In many investigations errors can be deduced at the beginning of the test. In this case the static head is the only unit measured in the investigation it has an error of:- ?Q = i 1 l/min The data obtained from the flow rate (Q) is used in the continuity equation to find velocity (V). As it has been established an error is found in the flow rate it is obvious then to state that there is an error in the velocity. To find the error in the velocity, it must be known that the proliferation of errors in a quotient is expressed by this formula. Conclusion After the analysing the data we have concluded that the error of our experiment has come to be 15. 4%. The percentage of confidence is 84. 6%, which is reasonably accurate. So our findings support the continuity equation. It is noted that velocity is proportional to the cross-sectional area of the duct, hence smaller the area, higher the velocity and vice-versa. This corresponds to the equation of continuity. It is also observed that when the velocity of fluid increases, the pressure decreases. Hence as the velocity of water in the venturi increased as it passed through the contraction, the pressure decreased and as the velocity decreased over a larger cross sectional area, the pressure increased. This proves Bernoullis theorem which states that at any point in a pipe through which a fluid is flowing, the sum of the pressure energy, the kinetic energy, and the potential energy of a given mass of the fluid is constant. This corresponds to the law of conservation of energy.

How to Answer Situational Interview Questions

How to Answer Situational Interview Questions In a job interview, you’re thoroughly prepared for the standard questions about your skills and your work history. You’ve got anecdotes that show off your leadership skills or your communication skills. Smooth sailing, right? Sure, until you get a question that’s a little off the map: â€Å"Here’s the situation. You have an angry client on the phone, an urgent email demanding your attention, and the fire alarm is going off. How do you handle this?† The answer to that question isn’t in your resume (at least not obviously so). It’s not one of the stories you rehearsed in your bathroom mirror this morning. So what does this kind of question achieve, and how do you tackle it?Situational interview questions are popular with interviewers because they unearth two immediate things about the interviewee:How quickly he or she thinks on their feet.How he or she approaches problem solving.These are interview skills that you can’t necessaril y drill ahead of time, without knowing the specifics of what the interviewer is going to ask. But we will walk through ways to recognize situational questions right away, and how to approach these questions on the spot.Situational vs. BehavioralSituational interview questions are slightly different from that other popular interview question type, the behavioral interview question. Both question types lure you away from the resume review template. Behavioral questions call for you to tell a story about something you’ve done, or a time you’ve faced a particular challenge. Telltale signs of a behavioral question:â€Å"Tell me about a time you†¦Ã¢â‚¬ Ã¢â‚¬Å"Describe a situation where you did†¦Ã¢â‚¬ Ã¢â‚¬Å"Give me an example of†¦Ã¢â‚¬ These all boil down to a very simple ask: â€Å"Tell me a story.† The Interview Guys recommend breaking each one down using the STAR method:What is the (brief) context for the story you’re about to tell? (the s ituation)What task did you need to complete, and what were the challenges/constraints?What did you do? (What action did you take?)What were the results? Be as specific as possible, and pull out any quantifiable results (sales, statistics, etc.) if available.Behavioral questions are ones that you can kind of anticipate ahead of time. If you come up with a few ready anecdotes for each of the skills you want to emphasize/the skills on your resume, you can shine those up ahead of time and get ready to pull them out at the right time.Situational questions are a little different. Instead of a story about how you did something, these questions want you to talk about how you would do something. Hallmarks of a situational interview question:â€Å"How would you handle†¦?†Ã¢â‚¬Å"What would you do if†¦?â€Å"What would happen if†¦?†Ã¢â‚¬Å"Here’s a hypothetical situation†¦Ã¢â‚¬ Hypothetical is the key word here, whether it’s explicitly mentioned o r not. Situational interview questions are almost always structured as scenario + â€Å"what would you do?† The interviewer isn’t necessarily interested in how you’ve handled things in the past, although your experience can certainly be used to inform your answer to this hypothetical question. Really, it’s a test of your critical thinking skills, and showing the interviewer that you can hear a situation that you may or may not have ever faced before, think fast, and come up with a satisfying solution. It also gives insight into your thought processes.How to Answer Situational Interview QuestionsThe first strategy for answering questions like these is to remember that it’s not a trick question. It’s not a gotcha. The interviewer didn’t wake up this morning and think, â€Å"I’m gonna mess with that dude’s interview just to throw him off his game.† It’s not a personal question, it’s a professional one- so before you answer, it’s important to take a deep breath and think logically.More often than not, the answer is going to be the one that lines up most with common sense. Think of it as a kind of role playing, except the role is your best professional self, not someone else.Your plan of attack for situational interview questions should be to follow these guidelines:Be a good listener. Make sure you understand what you’re being asked. If you want to clarify any points, ask a question or two. (This has an added bonus of giving you more time to chew over the question.)Be honest. Interviewers know when you’re only saying something because you know they want to hear it. None of us is as subtle or slick as we think we are.Be brief. This story doesn’t need additional characters, or big embellishments. Make sure you get right to the point.Be clear about actions you would take, and why.Be specific. Always tailor your answer to the job description and the skills t hat would be required.What NOT to Do and SayDon’t wing it. You may decide that since you can’t anticipate the specific question, you should go into it cold and let your instincts be your guide. Unless you have a small cricket friend accompanying you to the interview and whispering guidance, this is not a great plan. You can still practice common situational questions, and work on connecting your own experiences to them.Don’t ramble. â€Å"†¦So anyway, what was I saying before I went off on that tangent? Oh, right, how I’d organize a project. Organization is so important†¦umm†¦sorry, lost my train of thought.† Staying focused is key. You want to get in, answer the question, and get out. There are no bonus points for a novella-length answer.Don’t give a generic answer. You want to give specifics whenever possible. Maybe that’s saying, â€Å"I actually faced something similar, and I did X. Given the chance again, this is what I’d do differently.† Maybe it’s saying, â€Å"I know Job Corp values efficiency, so here’s how I’d improve that process.† Either way, you want the interviewer to know that you’re not answering questions in the void, you’re being thoughtful and describing how you would react in this particular job.Common Situational QuestionsNow that we’ve gone through some of the theory behind situational interview questions, let’s look at some common ones that you can use to frame your interview prep.Q: Say you’re leading a team on a project that has a very strict deadline. It’s looking like you may miss that deadline. How do you handle that?A: In a case like this, where the deadline might not be negotiable, I’d make sure there was a Plan B option in place, and make sure that communication is strong throughout the group to make sure everyone knows what that Plan B is if things don’t go according to plan. This is similar to a situation I faced in my current job, where a server failure meant that we wouldn’t be able to finalize a process on time. We ended up having to use a manual workaround to get the data in, and it took some epic overtime, but in the end we just made it. When a deadline is in jeopardy, you do what you need to do. Q: You and your boss don’t get along, and you find that your everyday tasks are not getting done because of this ongoing conflict. How would you handle that?A: In my experience, resolving conflicts before they blow up is one of the most important professional skills to have. I know how important it is to work with people of all different kinds of perspectives, so I’d try talking to my boss about our priorities, and about the best way to achieve them. I’d make sure to stay very neutral and professional, and try to open up a dialogue.Q: You get an email from an angry client complaining about service. What would you do to de fuse the situation?A: First, I’d make sure I understand why the client is upset, and what the root cause of the problem is. If I need to do more digging, I’d be very apologetic and let him or her know that I am looking into the issue, and will keep him or her posted. I’d be very careful to keep that line of communication open, so that even if I can’t fix the problem right away, the client knows that I’m working on it and that this is a priority for me and the company.See? There’s no magic to answering these. You just want to make sure that you have a clear answer that makes sense, and aligns with the brand you’re trying to convey in the interview. And although you can never tell exactly which (if any) situational questions you’ll get, you can start thinking ahead of time about what skills and priorities you want to emphasize in the interview.You got this- happy hypothetical-ing!

Cultural Critique Essay Example | Topics and Well Written Essays - 1000 words

Cultural Critique - Essay Example Jihad (holy, or religious, war) is waged by the mujahideen (‘strugglers’ or Muslim fighters). Jihad is now commonly linked with terrorism Terrorism (anti-state, state-sponsored, religious, etc.) has existed in every nation, state and society in some form or the other (physical, emotional, psychological, economic, biological, etc.) since times immemorial. It is inherently latent in basic human nature, only it varies in degree and form from individual to individual and situation to situation. Terrorism can be traced back to the ‘Before Common Era’, a non-religious alternative to the use of BC in designating the first period of the Gregorian Calendar. According to Encyclop?dia Britannica Online, â€Å"The ancient Greek historian Xenophon (c. 431–c. 350 BC) wrote of the effectiveness of psychological warfare against enemy populations. Roman emperors such as Tiberius (reigned ad 14–37) and Caligula (reigned ad 37–41) used banishment, expropr iation of property, and execution as means to discourage opposition to their rule.† The thread of terrorism relentlessly stretched and â€Å"In the summer of a.d. ... nce by local whites in a campaign of terrorist violence that overthrew the reconstructionist governments in the American South and re-established segregation† (Bryant 2002) and in â€Å"1898, 10 September, Empress Elisabeth of Bavaria of Austria-Hungary (commonly called "Sisi") was stabbed to death by a young Italian anarchist named Luigi Lucheni, in Geneva† (New York Times 7). Terrorist and destructive activities have been perpetrated by almost every sect and culture, be they in the garb of the Crusades (One to Nine), activities of the Jewish Zealots known as Sicarii, anti-colonial conflict between Ireland and the UK, Algeria and France and Vietnam and France and the United States, conflict between national groups such as Palestinians and Israelis, fighting between religious denominations such as Catholics and Protestants in Northern Ireland, internal conflicts between revolutionary forces and established governments such as the successor states of the former Yugoslavia , Indonesia, the Philippines, Nicaragua, El Salvador and Peru, fundamentalist religious ideological strifes such as ?amas and al-Qaeda, suicide bombing tactics by ?amas and Liberation Tigers of Tamil Elam, terrorist activities of the Japanese Red Army, Puerto Rican FALN, Palestine Liberation Organization, among others. It is amply evident that terrorism is not an exclusive trait of any particular socio-religious group, sect, nationality, etc. It is the manifestation of the frustrations of disgruntled maniacal or brainwashed minds which have been cunningly manipulated to serve the interests of terrorists in carrying out destructive acts. Terrorist has no face, persona, religion or morals. His only identity is terror. He is a misguided and misdirected, indeed mentally captivated, ‘victim’ primed for