14 June 2014

Bend It Like Beckham: Analyzing Beckham's Kick from Fluid Dynamics POV

Let the game begins. From now on till up to a month, sleep pattern for some people may change due to the hooking up to the tele to watch the World Cup Brazil 2014. Who wouldn't, as it's one of the most celebrated sports tournament around the globe apart from the Olympic Games. And it happens every 4 years, that's how you can use all the 'reserved energy' you've been saving after the previous one at South Africa!

Anyway, let's go back a little bit into the history. Way back, to more than a decade ago into one of the recorded event in the world of football (or soccer, for you lot in the States). Probably the most-studied kick in football history was David Beckham’s free-kick goal in the England-Greece World Cup qualifiers in 2001. The kick left his foot, it was high enough to pass over the screen of defenders, and spinning enough on a vertical axis to curve toward the corner of the goal. It appeared to be aimed above the goal, but suddenly slowed down dramatically in flight and fell into the upper corner of the goal. How do you explain this through fluid dynamics point of view?






Well, let's begin with what the concept truly lies. The keywords here : the ball, the flow, the air. Those who took Fluid Mechanics would've known this as the flow of solid particles through fluid medium. 

How can we analyze it? First, we need some of the important data, coz without it we can't deduce the observation quantitatively.
  • The speed of the ball = 36 m/s (as reported by literatures) 
  • The distance of the kick from the goal = 27 m. 
  • Surrounding pressure = 1 atm (a typical atmospheric level as I presumed it's not on top of the mountain!)
  • Surrounding temperature = unknown, but let's assume it was 25oC (or 298K).

Why do we need the pressure and temperature? Coz we wanna know the density and viscosity of air, which gives us:
  • Density = 1.20 kg/m3
  • Viscosity = 0.000018 kg/ms. 

What else do we need? Oh, the 'properties' of the ball itself. As FIFA-approved standard, let's take the ball as having:
  • Mass = 425 g (or 0.425 kg) 
  • Diameter  = 22 cm (or 0.22 m)

So, do we have enough information? What else we can assume to make our analysis easier (as what engineers would do!)? Well, let's assume that the stitching on the ball, spin, gravity and wind that influence the speed and curvature of the ball's flight path are initially disregarded. Otherwise, this preliminary analysis will be neverending!

Now, we have almost all the information ready. What's next? Let's sketch how the situation would possibly look schematically. One word of precaution here: in actual situation, the ball would move in a curved projectile mode, hence the effect of gravity must be considered (as the initial statement was 'fell into the upper corner of the goal'). But in this preliminary analysis, I assumed it moved in a straight line horizontally. 


Taking the 'control' area is surrounding the ball, as it moves very fast from Beck's foot towards the goal post, we can assume the buoyancy effect subjected onto the ball is very minimal (~ 0) in the vertical z direction. The affect of the gravity (i.e. weight, W) is also assumed to be negligible, as it was also in the vertical axis. Hence, the forces that involved during the kick is the force by Beck's (F) and the drag force due to the air that acted on the opposite direction (FD).

So, the equation would be: Force = Weight - Drag force - Bouyancy Force.

And eliminating the terms of W and FB:

Notice that the left hand side of the equation could be expanded to indicate the change in term of velocity. Why do we need to find the change in velocity? Coz that's what causes it to slow down and entered the goal.

Further expanding the equation, and integrate with respect to the boundaries involved, we will get this expression...


Now, before we solved to find the respective velocities, we gotta calculate the Reynolds number as we need to determine what would be the value of the drag coefficient (as you can see the term CD in the equation). At the beginning of the ball’s flight, the particle's Reynolds number is:

At this particular point, the Reynolds number is close to where there's a sudden change in the drag coefficient, as indicated by the diagram below. As the value is way below the limit of 0.1, for the purpose of evaluation we can assume CD ~ 0.1 for easy calculation.




Now, how to determine the change of velocity? If the ball slowed down, Re is lesser, therefore CD should be higher (based on the graph). Assume that this transition occur at halfway through the goal, therefore we need to find what would be the reduction in velocities. 

For the first half,



Which means, the ball lost about 5% of its initial velocity.

For the second half, the ball is slowing down. But as Re ~ 501,000, therefore it doesn't follow our initial guess (of CD would be higher); thus we can still use CD ~ 0.1 at this point. Therefore,



Which means, the ball lost another ~7% of its velocity.

In total the velocity of the ball decreases ~12% from the initial, which is considered appreciably a lot when it comes to velocity reduction! But of course, the actual speed of the ball once it reached the goal was much lesser than what we calculate here as the stitching on the ball, spin, gravity and wind effect all contribute towards the slowing down of the ball (which we initially assumed to be disregarded) - which could probably reach 20% reduction. Massive? of course.

The outcome? GOAL!


Anyway. The footballs used in the matches must qualify the approved criteria set by FIFA. Ever wonder what are the testing procedures that the manufacturers must abide in order for the ball to pass before it can enter the field? These are the typical quality they must follow:

26 May 2014

PROMO: A Chance to Become A CFD Expert (Graduate Assistantship)

This is a promotional material and a chance of a lifetime for those who would like to pursue their MSc study in Computational Fluid Dynamics (CFD). I am looking for a candidate who's interested in the area of Fluid Mechanics, material design and process development to undertake a minimum of 1.5-years period of a research project. 

Brief details are in the followings:
  1. Period of study: 1.5 - 2 years (depending on the depth of research).
  2. Scope of project: computer simulation/modelling, to design and develop channels for a gas system via computational fluid dynamics (CFD) approach.
  3. Funding mechanism: A fully-funded project under the Long-term Research Grant Scheme (LRGS) by the Ministry of Education. 
  4. Requirement: a Chem Eng graduate, with a minimum CGPA of 3.00. Preferably someone who has passion in the fluid mechanics, numerical methods and mathematics.
  5. Tuition fee: Conditionally waived.


What are the benefits?
  1. Opportunity to attend conferences/seminars - fully funded, local and overseas.
  2.  Since this project involved a multi-universities effort, you'll have a chance to be attend the Annual Colloquium organized by this research group (fully funded expenses).
  3. Prospect to become an expert in CFD, as it has recently become the most sought-after, go-to technology especially in Chemical / Mechanical/ Civil/ Petroleum Engineering.
Why CFD is now the most sought-after technology? What are the job prospects for you after the graduation that's related to CFD? 

For that matter, PM me if you're interested. 'Serious' candidate only.

~ zamriabdl@yahoo.com ~

16 May 2014

How Much Salt in Your Water?

Salinity is the measure of the salt content in water or soil. How much salt it contains depends largely on the source or origin of the water or soil itself. When it comes to salinity in water, various part of the water resources contributed to the various degree of salinity - which, in a typical research terms they are classified as either brine, saline, brackish or freshwater. The common unit for expressing the degree of salinity or concentration of salt is parts per thousands or ppt (not to be confuse with ppt of parts per trillion). 

The unit conversion: 1 ppt = 1 g/L. A typical seawater has a salinity of 35 g/L or 35 ppt.

Diagram below illustrates the variation of concentrations of salt (or degree of salinity) for various water resources.

[pix via wikipedia]

8 May 2014

I Should Talk More About My Research!

There're several comments I received last December during the final class evaluation exercise. Some of them clearly stated one recurring 'theme' of request : my research. Some wrote, "you should share more about your research in the class", "we want to hear more about your projects"... which somehow puzzling, given that my audience was still at their lower level of study. Some even came approached me and ask if they could get involved in my projects. The question that was swirling in my head after that session: what made them interested to know more about my research?

I think it's because of sharing. I shared some of my research output during the class session. Not a lot, but most of them were actually fly-off-the-wall remarks that just spontaneously popped into my head in that particular instance, especially when I was describing topics related to that specific field. For instance, when I talked about the flow through porous media, I relate it during which the incident I had upon designing the water filter long time ago and what caused it to happen. Or during when I was describing about pipe fittings, I mentioned the moment I had upon constructing my previous multiphase flow rig at UCL and how I used my previous technical knowledge to avoid greater turbulence in joining two pipes. Or the time when I was explaining the fluid flow through solid - I related it with how CFD could predict the flow phenomena, its flow streamline and all without even conducting experiment - and by which I also shared my CFD projects I did through the years. And many more instances, in which most of my sharing sessions with my audience were really very nonchalance - and they're all spontaneously done without me having any planned 'script' unlike the usual class' slides I'm showing on the screen. I can merely claimed they're somehow ad-libbed, as they're not part of my speech. Truly something that just sprung into mind, which somehow my brain cells get activated to relate the phrases I'm showing on the screen with what I previously encountered in my research works.

I think that's how they became intrigue... and excited to know more.

And IMO, that's what BigFat S.E.T blog should be too.... I should talk more about my research as the heading itself relates to 'Science, Engineering & Technology' after all. Well, I wish I could and I do want to. However, as what all research is about - especially the one regarding technical field such as science, engineering and technology - we're all bound to confidentiality. We're hooked into the clause of 'classified' issue, which became part and parcel that goes along with it. We can't talk everything that we have discovered freely, too discreet and specific openly; otherwise it would jeopardize the copyright and intellectual property of the project itself. 

Copyright, if we've published it into the journal or other technical publications - which somehow requires permission from the publisher themselves in order to share the full article apart from theirs (regardless it's we who wrote the articles anyway!). Intellectual property, if a project has yet to be filed for patent rights and such, which will violate its entire proprietary if we disclose to the public in its gory details. That's why whatever is gonna be shared have to looked upon, have to be aare and beware in order to protect the idea of oneself in its true form. Even if it's already being published, we're not revealing all as there're always an element of 'trade secrets' that went along with it to ensure the security of the knowledge. Public disclosure is too vulnerable, while secrecy is king. 

But anyhow, research is always exciting. And, yeah... I should talk more about my research here indeed. Not too specific, but more to generic, definitely!

13 April 2014

My Insider View: What Do They Ask During Professional Review Interview?



I previously received an email from someone who's about to attend the professional review interview (PRI) pretty soon. Fyi, PRI is the interview session for any budding engineers who intends to elevate their status and become a Professional Engineer, thus conferred the CEng at the end of their name. I received mine early this year after attending the interview session somewhere in late November 2013 (read some of my blogpost CLICK, CLICK).

One big questions that lingers in the head of those who'll be attending the interview is: what do they really ask during PRI? Well, to answer to that question this content of the email applies, and read what I replied.

~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~
The Question:

"Dear Zamri,
Hope you are doing well. I noticed that you were scheduled for the PRI session last Nov. I was just wondering if you would kindly share your experience with me on what took place during the PRI session and what was expected of you during the session. Also it would be greatly appreciated if you could shed some light on what sort of presentation method you had decided on using to present your case to the panel of assessors.  I am looking forward to hearing from you as I would genuinely like some feedback from you in order to prepare myself for the upcoming PRI session that I intend to attend. Hope to hear from you soon. Thank you. Regards."

~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~

The answer:

First and foremost, one has to understand that the PRI session is conducted by the Board members of the Institution (in my case the high committee of IMarEST Malaysia and UK), therefore they have to abide to the code of conduct and rules & regulations stipulated by the Engineering Council UK.

What is required for PRI?

1. Read through the documents from Engineering Council UK.
It is advised that the candidate to read through the documents available in the Engineering Council website. The reason being is that, Chartered Engineer status is conferred by the EC UK, therefore it's better to know what they are all about. Matters including the description on the Status of Engineers, Sustainability, Professional Ethics, UK-SPEC, etc should at least be familiarized with in the first place. [LINK].

2. Know the institution you're in.
PRI is conducted via the engineering institution you're registered with, such as IChemE, IMarEST, etc. Therefore, knowing what the particular institution is all about is essential. At least you acknowledge the Board of Directors and the Malaysian Branch's committee members; the vision and mission of the institution, and what they're aspire to become.


How the PRI is conducted and what sort of question being asked?

1. Interviewed by at least 2 panel members.
A typical interview session would involve a minimum of 2 panel members. I have gone through the PRI session twice last year: the first is somewhere in March where there're 4 panel members, and the one in November was by two panel members (by which one of them is the Vice President from the UK). The session will take about 1 to 1.5 hours, depending on how many questions asked and how detail you're describing and making your case.

2. Be prepared with a presentation material. 
Previously I didn't know that I had to present using a Powerpoint, therefore I had to just do it 'manually' i.e. talking with the aid of my printed hardcopy CV. If you bring your laptop or tablet with the related powerpoint slides, that is highly recommended. And don't forget to bring the printed CV as well, just in case the assessors wanna glance through to your particulars.

3. Distinguish the reason why you wanna become a Chartered Engineer? 
This is normally the 'ice-breaking' question and they will record what you're pointing out in their report. I think many candidate know why they wanna become a Chartered Engineer, but couldn't articulate it in a simplest way. Worse, if you're from the academic and research background like I am, coz we're unlike our engineer engineer at the plant or industries where different jobscopes are involved. But, if you can justify the reason and make a credible and distinct argument - you will excel, no doubt.

4. Make your case study. 
As the name 'engineer' is clearly spelled out in Chartered Engineer, you're expected to be involved with 'engineering tasks'. They will ask you to give examples on the projects/duties you did, the importance, their contribution, your level of involvement, etc. That's why if you have powerpoint slides it'll be much help, coz you can explain and show the evidences as many that you can recall as you want!

5. Acknowledge the ethos of 'Engineer'.
Expectation is always about: involvement with design and planning > procurement and finance > the benefit to the company you're in, the benefit to the society (if any). If you have examples to show such as process flow diagram (PFD), the plan, the design etc, then better bring it too (in the ppt slide, as long as it's not confidential).

6. Understand Sustainability.
One important question that become a MUST: Sustainability aspect. They will ask how sustainability involved in your daily engineering tasks. I think a lot of people don't truly comprehend the term 'sustainability' in term of its technical definition, and confuse it with the word 'sustain' alone, which typically relates to longevity or continuation of a certain resources. Yet, sustainability is beyond that - if you can understand the 'sustainability pyramid', then you are in a good place. One thing to be careful on this part of the interview: by any chance give a positive answer. Fail this, you might fail the whole interview!

7. How to achieve CPD.
Understand on what you wanna do after being conferred 'Chartered Engineer' and how would you carry out your CPD (the continuous professional development). State a clear, brief and concise examples on the various methods to achieve your CPD hours.
Last but not least, be prepared. And enjoy the session!

Zamri Abdullah CEng IMarEST