Page not getting refresh after form submission? - codeigniter

Question

<form id="contact-form" action="<?=site_url()?>/main/add_contact" onsubmit="return Validate()" method="POST">
<div class="inline-inputs">
<div class="col-lg-6 col-md-6 col-sm-12">
<label>Name*</label>
<input type="text" name="username" id="username">
<?php if ($this->session->flashdata('username')) {?><b style="color: red"><?=$this->session->flashdata('username')?></b><?php }?>
</div>
<div class="col-lg-6 col-md-6 col-sm-12">
<label>Phone*</label>
<input type="text" name="phone" id="phone">
<?php if ($this->session->flashdata('phone')) {?><b style="color: red"><?=$this->session->flashdata('phone')?></b><?php }?>
</div>
<div class="col-lg-6 col-md-6 col-sm-12">
<label>Email Address*</label>
<input type="email" name="email" id="email">
<?php if ($this->session->flashdata('email')) {?><b style="color: red"><?=$this->session->flashdata('email')?></b><?php }?>
</div>
<div class="col-lg-6 col-md-6 col-sm-12">
<label>Subject*</label>
<input type="text" name="subject" id="subject">
<?php if ($this->session->flashdata('subject')) {?><b style="color: red"><?=$this->session->flashdata('subject')?></b><?php }?>
</div>
<div class="col-lg-12 col-md-12 col-sm-12">
<label>Message*</label>
<textarea rows="10" cols="10" name="query" id="query"style = 'resize:none;'></textarea>
<?php if ($this->session->flashdata('query')) {?><b style="color: red"><?=$this->session->flashdata('query')?></b><?php }?>
</div>
</div>
<input type="submit" value="submit"/>
</form>
After this form submission the action goes to the method in the controller,there i have set with validation and kept
redirect(site_url().'/main/contact','refresh');
Even though the method exists in the controller why i dont no the page is not getting refresh after the form submission..
After the form submission the page should show the flash data,it is not getting refreshed,when i manually refresh the page after the submission then i can see the flashdata..